>> a chilling call, a horrifying discovery. >> my daughter, my son, my son-in-law. >> four people found dead, all shot. >> execution style? >> yes. >> a tragedy for one family. >> why my children? why? >> a puzzle for police because the killer left behind no clues. >> they're not going to solve this overnight. this is going to take a long time. >> who wanted these victims dead? one man did have a motive. >> nicole asked me, did nelson

serrano do it? >> but he also had an alibi. >> he was captured by security camera, hundreds of miles away. >> as the years went by and the trail grew colder, this veteran detective refused to give up. >> we just have to keep digging. >> over nine years and across two continents, he did keep digging. finally, he found the one small clue he needed. >> this is a bingo moment. >> it is, exactly. >> would it be enough to catch a killer? dennis murphy closes the book on "unfinished business." thanks for joining us. i'm ann curry. four people shot and left for dead, but the one man with a motive was 500 miles away that day. and for nearly a decade, the crime was unsolved. but one investigator refused to rest until he solved it, and he did. here's dennis murphy.

>> reporter: can you remember your 10th birthday? the cake, the anticipation of opening presents? the twins, mara and nicole, will never forget their 10th. sadly, it was december 3, 1997. >> just remember that we woke up and then he sang us happy birthday. >> he was their dad, 35-year-old frank dosso. any special plans for that day that you remember? >> that night, we were supposed to have cake and coffee with our grandparents and our aunt and uncle and my mom and dad. >> reporter: but their father was late getting back from work, unlike him. frank had promised his wife maria he'd bring home chinese for the party. >> at a quarter to 6:00 i called him, because i was actually annoyed with him. i was going to say to him, why aren't you home yet? of all days, you know, you're coming home late. how are we going pull this off? we don't have our food, our dinner, and there was no answer already. >> reporter: maria began to worry. maybe there had been car

trouble. worse, an accident. >> whoa. >> reporter: frank worked with his father and sister's husband at a manufacturing business in central florida near tampa. they made the kind of conveyer systems you see in dry cleaners that retrieve garments. but now, on the twins' birthday, it was getting late. the last time they talked, frank told maria that his sister, diane, would be picking up him and her husband, george patisso. they'd all arrive together. but where were they? when did you know something was wrong, something terrible? >> i think when my mom started getting nervous. >> so 6:00, no frank, you're starting to wonder? >> i had a lump in my throat. i was a nervous wreck. >> what were you worried about? >> because it was unusual for frank to be 45 minutes late and not tell me that he was going to be late. >> reporter: maria dosso called her husband's parents, phil and nicoletta. they hadn't heard from their son or daughter either. so the elderly dossos got in their car about 6:30 p.m. and drove 20 miles to the shop, erie

manufacturing. the lights were on. they saw their daughter, diane's, car parked out front. >> i walked in, the door was open. it was not locked. i walked in there and i saw diane. i said, my god, diane, who did this to you? who did this to you? >> reporter: the parents saw their daughter diane first in the hallway, her legs crumpled beneath her in a pool of blood. she'd been shot twice in the head. around the corner, more. diane's husband, murdered execution-style. his body was slumped by dosso's long-time business partner, george gonsalves. and a few feet away lay their son frank, maria's husband, the twins' father, like the others, shot in the head. >> my daughter, my son, my son-in-law and my partner, they're all dead! >> and then the police came and everything. i don't know anymore. i said to the police, let me stay until you take them out. let me see them the last minute

until you go out. no, no, they said, no, no, you can't stay here. you can't stay here. so i called diane, and i said i was the first one to see you coming in and i'm the first one to see you going. and i closed the eyes. >> reporter: it wasn't long after frank's wife maria arrived to flashing lights and strung yellow crime scene tape. her father-in-law delivered the unbearable news. >> phil came over to me and held me so tight, it hurt. he held me so tight. and he told me, maria, we lost them. >> four dead, four murdered. an extended family's gaping horror became an urgent criminal investigation. polk county, florida, the town of bartow, had never had a crime like it, a mass murder. there were so many scenarios to run down. was it an act of passion, perhaps, or revenge? was diane, the dossos' daughter,

who happened to be a local prosecutor, the target? local police quickly called on the help of agents from the florida department of law enforcement, the fdle, the state's counterpart of the fbi. fdle agent tommy ray was put in command of a state local task force. >> when we first started the task force, we started looking at this, there was an fbi profile. he stated that this was a clear case. and i said, what do you mean a clear case? he goes, hopefully you'll solve this but you're not going to solve this overnight. this is going to take a long time. >> reporter: agent ray knew all about crimes taking a long time to crack. in his 25 years on the job, he had a well-earned reputation as a cop with a knack for solving stone-cold cases. hopefully, the erie manufacturing massacre wouldn't be one of them. detectives began their investigation by looking at what the crime scene itself could tell them.

the warren of offices and hallways in the shop where forensic technicians recovered 12 bullet casings, 11 of them .22 caliber, the other, a .32. that meant two different guns had been used. >> initially, we thought there was more than one shooter. we thought it was probably two to three suspects. >> reporter: from the trajectory of the wounds in the victim and resulting blood spatter no more than a foot or so off the ground, the investigators concluded the three men had been forced to their knees or put on the ground and killed with a .22. >> you could see how someone in the doorway with a firearm could hold three guys at bay, maybe force them down and as they were getting down, start shooting. >> reporter: diane, the evidence suggested, had apparently come in after the initial murders and chased by her killer and grabbed from behind by the hair. she'd been shot in each temple with both a .22 and a .32 caliber handgun. but fingerprints, dna, hair, fiber, the killer or killers hadn't left a trace. there was a chair with a dusty footprint of a man's shoe on it

and a dropped ceiling tile overhead that had been moved. but like so much else about the puzzling scene, detectives didn't know what to make of it. four families shattered. maria dosso was suddenly the single parent of three young girls. >> and i remember we were all in -- lying in their father's bed, just -- just holding each other, and i didn't want to change the sheets for a while because that's the bed that frank had slept in. i just wanted to hold onto whatever i could. and i think the girls wanted that, you know? we just wanted to feel as close to him as possible. and i guess the sheets that he had slept in would have been it. >> how did you tell the girls? >> i told them one by one. i remember nicole was the first one. and i told her, i said, you know, daddy, you know, is dead. and the first thing nicole asked me, did nelson serrano do it? when we come back, police were soon asking that same question. but could how could this man

have killed four people in florida when this tape shows him 500 miles away shortly before the murders? >> the detectives felt it's impossible for him to have made it back. >> maybe, maybe not, when "unfinished business" continues. [ shapiro ] at legalzoom, you can take care of virtually all your important legal matters in just minutes. now it's quicker and easier for you to start your business... protect your family... and launch your dreams. at legalzoom.com we put the law on your side.

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the three partners who made up erie manufacturing were like family. they danced at weddings of one another's children. in 1985, when frank dosso married maria, business partner nelson serrano was there celebrating with his wife.

serrano, originally from ecuador, had been a middleman who sold the garment conveyer systems that erie made to big customers. eventually, he bought into the company and was welcomed as a full partner of phil dosso and his long-time friend and co-founder of erie, george gonsalves. with serrano's flair for sales, and the original partner's knowledge of the nuts and bolts of manufacturing, the company grew into a multimillion dollar family operation by the middle of the '90s. so times were good? >> yeah, they were good. >> reporter: they got better and better. they were making way for the children to take over for frank. there was something about serrano that spelled trouble for his wife. >> he always thought he was better than everyone else. >> reporter: and she wasn't the only one that felt that way. by the summer of 1997, a long-simmering dispute among the partners had boiled over into an all out wa- out warout war.

there were allegations that nelson serrano had stolen a quarter of a million dollars. after threatening lawsuits and one shouting match too many, the founding partners, dosso and gonsalves, fired serrano and his son and then they changed the locks to the office. but serrano didn't leave quietly. within weeks of being ousted, he tried to force his way back into the building. partner george gonsalves called the cops. >> 911 emergency. do you need police, fire or ambulance? >> someone's breaking a door down. >> is it someone you know or a former employee or what? >> yes, former employee. >> okay, what is his name? >> nelson serrano. >> reporter: then six months later, december 3, 1997, came another 911 call from erie manufacturing. four dead, shot execution style. given serrano's stormy relationship with his partners, homicide detectives asked him to give a taped statement the day

after the killings. >> i have no idea what even happened, where it happened, when it happened, how it happened. >> reporter: serrano talked to police willingly, sharing details of a business partnership gone awry. >> we never had any problems until we started making serious money. >> reporter: even speculating on how the murders went down. >> there were many people involved. i mean there are four people in there. one guy is going to go over there and kill four people? >> reporter: serrano told police he was in atlanta, 500 miles away from erie manufacturing, on the day of the murders, holed up in his motel room, door locked, drapes pulled suffering from a migraine. and an airport hotel security camera seemed to bear his story out. here he is on tape at an atlanta la quinta inn, in the lobby, around noon on the day of the massacre. he walks into frame again about 10:00 that night. agent tommy ray's team, of course, had his alibi checked out. >> we got a phone call from the

two detectives that went up to atlanta, they said hey, we have got him here in the afternoon. he couldn't have done it. >> reporter: but that didn't mean the detectives thought serrano's hands were clean of the crime. >> we believe that nelson was in atlanta and that he had hired someone for a contract killing. >> reporter: for all the red flags flapping around them, detectives never could get enough to arrest nelson serrano. years went by. the twins had other birthdays. nicoletta dosso dressed only in black, a perpetual state of mourning for her murdered son and daughter. you said during this ordeal, you lost your faith in god. did you get it back? >> well, a little bit at a time. a little bit at a time. why my children? why? they didn't do nothing wrong, why my children? >> reporter: and the father of one of the murder victims, diane's husband george, flew to florida to demand answers from prosecutors but got unpromising replies. >> they told us that even though

they had been working on it for a couple of years and they had many leads, we just want you to understand that there's a possibility that this case will never be solved. >> reporter: but agent tommy ray, the chief investigator, hadn't thrown in the towel. in fact, he made a promise to the victims' families, including the mother of george patisso. >> he said he would never retire until this was solved. he lived and breathed this case. >> reporter: but tenacity and resolve weren't the same thing as results. here was the detective's problem. he'd come to believe that it was serrano himself who walked into erie manufacturing and shot the four. but nelson serrano's alibi had him up here at the atlanta hotel on noon of that day. the killings happened about 5:30 in the afternoon way down here. so, how did serrano get from atlanta to erie manufacturing in florida and back to atlanta in time to be photographed by the hotel security camera again at 10:00 or so? he had to fly, obviously. but only two airports in central florida made sense for the very tight timeline of the crime to

work. he either flew into orlando or into tampa. all theory. meanwhile, the murder investigation at erie manufacturing was getting colder and colder. this case then hit a brick wall, huh? >> as far as a brick wall, we were still doing background on any and everybody connected to nelson serrano. >> reporter: one of those people connected to serrano was a nephew in florida named alvaro penaherrera. the detective could not figure out why serrano had called his nephew so frequently around the time of the murders. >> the day of the homicide, nelson had called alvaro around 7:53 a.m. there was a series of phone calls that connected alvaro to nelson. >> reporter: then detective ray's team came up with a bingo moment, the discovery of a credit card transaction for serrano's nephew on a most interesting day and for the detective in a most interesting place. >> he rented a car on december

3rd of '97, the day of the homicide. it was rented in orlando, but yet turned in in tampa. >> reporter: when the detective brought the nephew in for questionig, tommy ray said the young man lied about the car rental at first, then caved when he feared he might become a suspect in the mass homicide. >> his uncle, nelson serrano, called him and said, look, i need you to rent a car for me for december 3rd. i mean, i'm having a brazilian mistress that's flying in and i don't want my wife to find out about it. >> reporter: but another problem. if serrano flew to orlando that day to pick up a rental car from his nephew, he didn't fly under his own name. there was no serrano on the passenger manifest of the only flight that day from atlanta that fit the timeline. but a few weeks earlier in a casual conversation, the detective learned from the dosso family that serrano had a child from an early marriage who was rarely mentioned. and what was a name associated with that child? >> juan agacio.

>> reporter: agacio, that was a name on the passenger manifest from atlanta to orlando the day of the murders. and agacio ,who paid cash for a roundtrip ticket and never used the return portion. and what's more, someone named john white had done the same thing, bought a roundtrip ticket for cash from tampa to atlanta for the evening of the murder. and like agacio, he'd never used the return fare. agacio, white. a nephew instructed to arrange for a rental car for orlando, one dropped off at tampa airport. the pieces were snapping into place for tommy ray. here's what ray was thinking. serrano, using an alias, flew from atlanta to orlando, picked up the rental car and drove to erie manufacturing and committed the murders. then he drove to tampa, dropped the car off and returned to atlanta using another alias all in the ten hours allotted, all done in a calculated way to cover his tracks.

so, do you go to the prosecutor at that point and say, we got it, let's go to the grand jury, let's get an indictment? >> yes. >> and he said? >> he said, you're close, but you're not there. need a little bit more. >> what's he need? >> he needs something placing nelson, an eyewitness, some physical evidence, something placing nelson back in the area on the day of the homicide. >> do you think you were ever going to get more than you had? >> oh, yeah. we knew this was just beginning. there's more out there we have to keep digging. >> reporter: digging. it's in the detective's dna. and now the erie murders would find him digging through a box of moldy, old receipts. like little jack horner, tommy ray pulled out a plum. when we return, the detective's discovery. would it help him catch a killer? >> divine intervention plays a big part in here. >> but just when he thought the case was solved, his suspect slipped away again, when "unfinished business" continues. [ male announcer ] want a better way to track what you spend? pnc virtual wallet now comes with spending zone.

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hey there everyone, i'm alex witt. here is what is happening. deadly violence continues to take a terrifying toll in syria after at least 57 civil yaps have been killed in armored assaults across the country. among them, 38 in the eastern city of deir el-dour. demonstrations in london erupted into a riot thursday. protesters threw moltov cocktails and looted buildings. 26 police officers were injured in the arrest. more on that later. now, back to more "unfinished business" here on msnbc. reporter: the company made garment conveying systems and sold them for millions every year.

in the halls of the business office of erie manufacturing, four people, three men and a woman, had been shot dead. florida state detective agent tommy ray thought he could prove that nelson serrano, an ousted business partner, had done it, even though he claimed to be in atlanta that day and a hotel security camera backed that story up. he's got a good alibi, doesn't he? he's 500 miles away. >> he had planned it out well. >> reporter: detective tommy ray had evidence indicating that serrano's nephew left him a rental car in the orlando airport parking garage. he put the ticket to get out of long-term parking in the visor. that meant that serrano had to have touched it. but where was that years old ticket now? did it still exist? the detective had to get his hands on it. but big problem at the airport records office. >> initially, a couple of the other detectives were told that those particular tickets had been destroyed by a storm. >> you must have thought that

somebody was playing games on you, huh? >> we thought, there's no way our luck could be that bad. >> reporter: but tommy ray kept on coming. that parking ticket might be his only shot at proving that serrano had indeed put foot back in florida the afternoon of the murders. insisting -- >> i said, i want to see where the tickets were destroyed. i want to see what you have. >> reporter: and as the detective was getting ready to go to the airport, he got a call back from airport officials saying, sorry, they were wrong about those tickets being damaged in the storm and they were, in fact, intact and waiting for him to sift through. so now you're on the flip side of this luck, huh? >> divine intervention plays a big part in here. >> reporter: ray and his team tediously pored over hundreds of old parking slips. and finally, there it was. a car had left the long-term parking garage at 3:49 p.m. and printed right on the receipt, the license plate of the rental car picked up by serrano's nephew.

and when the fingerprint expert at the state crime lab started processing that 3-year-old parking receipt, a wondrous thing happened for tommy ray's blossoming theory of the case. >> lynn called up and said, tommy, i've got some fantastic news. the fantastic news was that we had prints of nelson serrano. >> reporter: the fingerprint proves that serrano was in florida on december 3rd, 1997, just an hour and a half drive away from erie manufacturing. not in a hotel room in atlanta nursing a migraine. >> i knew at that point, that was more than enough for an arrest and an indictment against nelson serrano. >> reporter: and in may 2002, almost 4 1/2 years after the murders, tommy ray finally got his indictment, four counts of first-degree murder against nelson serrano. but there's a problem. you can't arrest him, right? >> nelson fled to ecuador. >> reporter: federal officials said the chances of extraditing serrano, an ecuadorian national, would be slim to none.

the detective's superiors told him to forget about it. so their answer to you was close but no cigar? forget about this one. >> get on another case. >> when somebody tells you forget about a case, is that an order that sticks? >> not really, especially in this case. >> reporter: but orders were orders and ray got new ones. a re-assignment to miami. but luck followed the detective to miami where a chance meeting with an ecuadorian colonel soon changed everything. ray asked the colonel to convince his government to extradite serrano, and told him why he wanted him back so badly. >> after he saw the violence and, you know, what nelson serrano had committed, he said, we'll work it out. we'll get him out of ecuador. we'll get him out of ecuador. >> reporter: and that's just what tommy ray did, with the full cooperation of ecuadorian authorities. when officials there discovered serrano had actually been a u.s. citizen for years, they deported him to america in the custody of detective ray.

in september 2002, nelson serrano walked into a central florida courtroom and pleaded not guilty to the murder charges. after a snarl of legal delays, in september 2006, nearly nine years after the murders, serrano finally sat before a jury, the accused, in a first-degree murder death penalty case. >> that man sitting right there murdered four people. >> reporter: in court, tommy ray sat a few feet away from nelson serrano. the families of the four victims packed one side of the courtroom as the prosecutor, john aguero, called phil dosso to recount the history of bad blood with serrano. >> he said i don't want to see your face anymore. because i can kill you someday. >> reporter: the voice of the mother of two of the victims took jurors back to the horrors of the night captured on that 911 call. >> we're at erie manufacturing.

>> reporter: the prosecutor introduced the gruesome crime scene photos, bullet casings and bodies that accompanied the story that he told the jury about a one-time business partner's homicidal revenge, the bitter loser in a fight for control of the company. and when jurors went to tour the murder scene itself, the prosecution explained its theory of why that ceiling tile had been moved and why there was a dusty footprint on the chair beneath. employees testified that serrano, a gun enthusiast, kept handguns in his office and may have stashed at least one away in the dropped ceiling. >> same day you see him getting something out of the ceiling is the day you see the gun? >> yes. >> reporter: behind the tile, likely prosecutors say where he kept the .32, one of the two guns used that night. >> there was only one person that we heard about that would have an interest in that ceiling tile and that's the guy that maybe left a gun up there that he don't want the cops to find. >> reporter: and as for the dusty shoe print, not

definitively serrano's, but very much like one he once owned and experts examined. >> the wear pattern is consistent with the shoe that stepped on that vinyl chair in december of 1997? >> absolutely. >> reporter: prosecutors knew they would have to shred serrano's alibi that he was in atlanta for a business trip and not in florida for the lethal business of murder. >> people would go to atlanta, they would find him on the videotape, he would be alibied and nobody would ever look any further. and that would be the end of it. in terms of being diabolical, that's a pretty good alibi. >> reporter: they laid out their evidence for serrano being in florida that day. they called the nephew who rented a car for his uncle and he told a damaging story. the day after the murders, he said his uncle ordered him to retrieve that same car in the tampa airport parking garage and drop it off at the rental company.

weeks later, the uncle told the nephew to keep his mouth shut about the incident. >> he said you can't say anything about this, you know that. first, it could jeopardize my marriage and, second, the cops are not going to buy it with the lawyers. they're going to try to do something to me. >> reporter: and the prosecution played maybe its best evidence. played maybe its best evidence. the orlando airport date-stamped parking ticket with nelson serrano's fingerprints on it. >> there's no doubt that that man left that fingerprint on that card? >> no, sir. >> the only way it could have gotten there is if nelson serrano's index finger touched the card? >> yes. >> reporter: and prosecutors especially wanted jurors to listen closely to that taped statement that serrano gave police the day after the murders. it was weirdly as though he were reciting the state's own theory of the crime. >> i don't think it was a robbery.

>> reporter: and listen further urged the prosecutor to what nelson serrano had to say about why diane patisso was murdered when she went to pick up her husband and brother. >> he says i think the girl walked in on something. wait a minute. nobody's been in this crime scene. >> so this guy knows information that's only available to arriving officers, medical personnel? >> right. it's certainly not been put out on tv, nobody knows where these people were. and he's making this statement. >> reporter: the investigators never did find the two handguns used in the killings, but as it rested its case, the prosecution was comfortable in thinking they had convinced the jury they could have only been in the hands of nelson serrano. >> that's one diabolical son of a gun sitting over there. >> reporter: a one-time partner, the prosecution argued, with a wounded pride and a murderous

rage. when we come back, was there enough time for nelson serrano to commit four murders? the defense says no. >> i challenge anybody to show me. i'll pay them a million dollars if they can do it. >> if they can do that in the time allotted? >> can't happen, didn't happen. >> when "unfinished business" continues. five chicken breasts individually wrapped, so you can use what you want and put the rest in the refrigerator. and the best part is it only takes 10 minutes. it's my go-to meal. matter which position i am in i wake up feeling good. it fits you so perfectly... it fits you. you wake up and you're revived and rejuvenated. it's just like wow! tempur-pedic the most highly recommended bed in america. tempur-pedic is rated #1 in comfort. sleep satisfaction. and back support. it fits the curvature of your body but you don't sink in and it is firm.

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the heart of nelson serrano's defense was simple. there's no evidence to prove that serrano ever set foot in erie manufacturing the day of the murders. what was the biggest obstacle in trial you had to overcome here? >> the biggest obstacle is four dead people. it's a lot easier for jurors to find somebody guilty on maybe evidence they're not supposed to.

>> reporter: defense team bob norgard and cheney mason were relentless in their cross-examinations of witnesses, starting with the investigators who gathered evidence. 12 bullet casings, for instance, told them nothing about who loaded the guns. >> with respect to the casings, no fingerprint evidence linking those casings to mr. serrano? >> that's right. >> reporter: no serrano fingerprints found anywhere around the crime scene. >> not a single fingerprint was linked to mr. serrano in that building, isn't that true? >> none of the fingerprints were linked to him. >> reporter: the dusty shoeprint seemed to be serrano's shoe size. >> can you tell me how many shoes there are that match -- >> no, i cannot. >> 2 million, 10 million, 100 million? do you know? >> i really don't know. >> this is all part of a circumstantial case. you have to believe each link in the chain to get him to make that footprint in the chair. >> what is the theory here? there are three men in there, 200-plus pounds each. excuse me, fellas. i need to borrow this chair so i

can climb up there and get a gun so i can shoot you with it. how silly is this? >> reporter: serrano's son, francisco, had been called by the prosecution, but the defense used him to flip the tables, testifying that it was his father's partners who actually stole business money from him, not the other way around. >> a million dollars had disappeared. and george and phil were not willing to tell us what they did with the money. >> reporter: then the defense went after the busy here, there and everywhere of serrano's alleged travels the day of the murders. in and out of airports, boarding planes, driving around. how come no person or camera saw him? >> not a single witness was found who saw mr. serrano leave that hotel, drive to the airport, park at the airport and get on a plane, isn't that true? >> that's correct. >> and you're sure that there are no videotapes from atlanta, tampa or orlando showing mr. serrano anywhere near those airports on this day, isn't that true? >> i have no personal knowledge

of any tapes of that nature, no, sir. >> reporter: and in that day of travel, the defense argued that there just wasn't enough time for serrano to have pulled off the crime he was charged with. leaving the orlando airport garage at 3:49 p.m., as the time-coded parking record indicated. as detective tommy ray testified, it had taken him an hour and 15 minutes to drive from the airport to erie manufacturing. that would have put serrano at the shop just after 5:00 p.m., leaving him only 15 minutes to kill four people. your important part of the timeline is look when the last victim is killed. it has to be 5:20? >> you'd be stretching your imagination to believe that you could drive that distance in the traffic and get there and be able to commit these crimes. i do not think so. >> reporter: and the last part of the timeline, the defense argued, is more than implausible. in less than a half hour, serrano would have to get off a wide-bodied jet, exit atlanta airport, one of the busiest in the world, and arrive back at

his hotel five miles away, all in time to be photographed looking up at that surveillance camera. >> i'll challenge anybody to show me -- i'll pay them a million dollars if they can do it. >> if they can do that in the time allotted? >> 28 minutes. can't happen, didn't happen. >> reporter: the biggest hurdle for the defense is just ahead. starting with the testimony given by the nephew that he had arranged a car rental at the orlando airport for his uncle on the qt. the defense grilled the nephew, portraying him as somebody who was just interested in saving his own skin. >> you weren't just someone they wanted to question as a witness but they had you pegged as a suspect in a quadruple homicide, isn't that true? >> yes. >> you want to tell the jury how much that scared you? >> i have to say i was very scared. >> so they broke you down and got you to change the story, right? >> yes, i changed the story. >> reporter: in a circumstantial case, that the prosecution had the burden of proving beyond a reasonable doubt, it came down to one crucial piece of evidence, nothing less than the

foundation of the prosecution's charges against nelson serrano, his fingerprint on that parking ticket that put him in florida on the afternoon of the murders. the state had put on three fingerprint experts. two agreed that it was serrano's, but the third surprised the prosecutor, when under cross-examination, he testified he wasn't entirely convinced. >> i had and i still have reservations about this particular latent. >> reporter: an expert in the field, the prosecution's own witness telling the court he had reservations about the fingerprint. why, he wondered, was a finger from serrano's right hand on the ticket and not one from his left. >> if you're wearing a seat belt, it's extremely restrictive, where you are reaching across your body, between your body and the steering wheel, to hand it to someone over here. >> reporter: the defense leaped into the crack in the prosecution's case and floated the possibility that the all-important fingerprint was bogus, forged by a person or persons unknown to implicate serrano in the crime.

>> were you able to determine from them anything about the veracity of those prints? >> no, i can't. >> can fingerprints be planted and not detected, even by experts? >> i had a great deal of experience with the so-called forged and altered fingerprints. >> are you saying that the cops did it? >> i don't know who. the cops planted a bogus fingerprints on this -- there's a high likelihood that that print was an act of desperation after years of frustration in this very high profile, very significant case. >> reporter: had the defense made the jury wonder? had they put some cracks in the prosecution's theory of the crime? after 60 witnesses, 400 exhibits, five weeks of trial, closing arguments were at hand, the defense going first. >> not a single person on the planet earth, not one single person has put mr. serrano at

erie manufacturing on december 3, 1997. >> reporter: the prosecutor countered that serrano had a volcanic grudge against his former business partners and the parking ticket and the long chain of circumstantial evidence was the proof that he was the killer. >> it's getting harder and harder and harder to think that all of these things could just be coincidences and they happened to poor mr. serrano. that's one diabolical son of a gun sitting over there. >> reporter: it was now up to a jury to decide. >> there was no evidence, no witness to put him in polk county, none of those things. and keeping an open mind, he was still innocent. when we return, as the jurors begin to weigh nelson serrano's fate, it is clear the decision could go either way. >> how many of you were right on the line and didn't know where you were going to vote? show of hands. >> when "unfinished business"

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the judge stood up and said this is a trial for four counts of murder that were for the death penalty. my jaw just dropped. >> reporter: no juror had bargained for this when they got their summons, potentially a death penalty case. and looking over at the defense table and seeing nelson serrano, the accusation didn't seem to fit. >> i was like, oh, that must be an attorney. >> it's kind of an older guy in a suit and tie and he's accused of this horrendous massacre.

>> definitely didn't look like someone that would do that. >> we gathered 8 of the 12 jurors to talk about the case, starting with the prosecution's four-hour opening statement that left some jurors scratching their heads. >> it was very complex when he went through the long opening statements. and it was a little hard to put it together. there was some holes in it. >> it's a very complicated story, isn't it, what happened at this business and there were a lot of names? >> in the beginning, it didn't make sense. >> reporter: jurors said the defense attorney cheney mason made it shorter and simpler for them to understand. they said, my client, the defendant, nelson serrano, wasn't at that place, can't put a gun in his hand, there's no hair, fiber, fingerprints, dna. there's nothing to indicate he was in that place on that day. >> they had me, they said he didn't have a gun, he didn't have this. you can't prove that he was there. >> reporter: more important from the assertions from both sides was the evidence in the case. a visit to the crime scene was a

jolt for jurors. they literally walked in the killer's footsteps at erie manufacturing. >> the word "erie" was very fitting that day. >> lucy, was it chilling for you to walk into this place? >> yes, especially the office where the three gentlemen were. it was much smaller in person than i felt it was in the pictures. and just being in there, i wanted to get out. >> reporter: there they saw the ceiling tile that had been moved, where serrano had been accused of hiding a gun used in the murders. but as for a supposedly telltale dusty footprint on a chair beneath that tile, some jurors dismissed it as evidence. >> it shouldn't make no difference whatsoever to me. >> reporter: but what preoccupied jurors most was the tight time line of the theory of the crime. just ten hours for serrano to fly, drive, murder, fly again and be back in atlanta and be photographed by a hotel security camera. a complicated scheme, wasn't it? >> it was crazy. i mean, it was only ten hours.

>> we all travel, we know it's a nightmare getting in and out of airports. did anybody have trouble with these whole orchestrated events? anybody doubt that it could be done? >> i did. just the simple fact that there was no evidence, no witness to put him in polk county, none of those things, and keeping in -- an open mind, he was still innocent. >> reporter: jurors also weighed whether serrano's nephew was a possible suspect as the defense suggested. after all, the nephew had not only rented the car, he also admitted to lying to investigators early on. do you think he was in on it at all, the nephew? >> no, i don't. >> none of you do? >> nelson serrano hung him out to dry. >> reporter: and finally, jurors had to evaluate probably the most important evidence in the case, that fingerprint on the parking lot ticket from the orlando airport. jurors heard two experts say it was serrano's, but another opened the door to doubt,

conceding under defense questioning that the print could have been planted. >> i had my reservations about it. it made me second guess it. >> if it's forged, does the case fall apart? >> that would be the one that the defense was knocked out of the park. >> and here is this very well-credentialed expert telling you, i don't know. i've got reservations about it. >> that would have been strong evidence that he was not in florida. >> reporter: after seven weeks of trial, serrano's very life hung in the balance. the jurors, still unsure themselves at the end of testimony what side they'd come down on. a show of hands question. when the defense sat down in their closing argument to you, how many of you were right on the line and didn't know where you were going to vote? show of hands. this was innocent until proven guilty still until that moment? >> yes. when we return, the tension in the courtroom as the jury hands in its verdict. >> all rise, please. >> when "unfinished business" >> when "unfinished business" continues. [ man ] i got this new citi thankyou card

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reporter: the jury was out. stretched nerve endings got rawer yet. four victims, four families. they had waited for this moment for nine years, but neither they, nor serrano's family, would have to wait much longer. after six hours of deliberations, a verdict. anticipation outside the courtroom. even tommy ray, the cold case cop who pursued serrano for so long, looked frazzled. >> all rise, please. >> reporter: the jurors filed back, the families held hands, braced. the defendant stood as the judge read the verdict. >> count one, the defendant is guilty of first-degree murder. count two, the defendant is guilty. count three, guilty. count four, guilty.

>> reporter: serrano never flinched. the families' gasps were silent but the relief was visible. in the end, jurors say they didn't buy the defense argument that serrano couldn't have had enough time to travel and commit the crime all inside ten hours. >> there was plenty of time to do what he wanted to do. >> reporter: the other thing critical to their conviction, serrano's fingerprint. >> his alibi was shot with that fingerprint on the parking ticket. >> reporter: outside the courtroom, it was as though the families were finally able to have the wake they had been denied all these years. the dossos, who lost their son, frank, and their daughter, diane. >> now he's suffering for what what he did to my kids. he took everything away from me. >> reporter: the patissos, who lost their son, george. >> nine years but we got him. >> reporter: and the grieving widow of the partner in the business, george gonsalves. and then there was maria and her three girls. they lost their father on, of all days, the twins' birthday.

the twins will have their birthday tainted as long as they live. >> yeah, they don't want to celebrate their birthday on december 3rd anymore. i told them it was the day. it was the date i started dating their father and the day they were born. we couldn't focus on that day as just being the tragic day that it was. >> reporter: tommy ray, the detective who never gave up, closed a chapter of his life. almost a decade pursuing a man who said in the first hours of the investigation that they'd never catch the one who did it. >> look at the family. it's all about them and finally they're getting justice, after all these years. >> reporter: agent tommy ray promised the families he'd never retire before this case was over. now, finally he could, the man who kept on coming. >> finally. finally. in june 2007, nelson serrano received four death sentences. like all death penalty convictions in florida, serrano's case is automatically being appealed.