i'm craig melvin. >> and i'm natalie morales. >> and this is "dateline." >> it's been extremely hard. >> the hardest part was the crime scene picture of our mom. >> i always told myself she didn't see it coming. >> reporter: a mother, at work in her office -- murdered. >> someone shot her and just let her die. >> reporter: four bullets. making sure she was dead. >> who wanted this very nice, professional woman dead? >> reporter: police start to dig. her new fiance -- >> he was like, i have to move on. >> it was just very suspicious.

>> reporter: her final client. >> he owned a .9-millimeter gun. >> reporter: and she was shot with one of those. her ex-husband. he was under deep suspicion by the whole town. >> he was. >> did you murder your wife? >> no. >> i know anyone's capable of anything but we would know. we're his kids. >> reporter: a chilling case. >> greed, hate, murder. >> reporter: with a riveting end. >> our mom's killer is still out there. hello and welcome to "dateline. "pam zimmerman was everything to her three children. cheerleader, confidant, mentor, a reassuring presence who was always there. then, she was gone, shot dead in her office. but why? in the search for clues, detectives focused on the men in pam's life and the secrets they kept. only one would face trial for her murder.

and the stunning outcome would tear pam's family apart. here's keith morrison with "before midnight." >> reporter: a few minutes after sunrise on the morning of november 4th, 2014, david zimmerman rose from his bed in a quiet suburb of bloomington, illinois. eager to dispose of the small worry that had been nagging at him all night, he padded across the room to his bedroom door. >> i woke up and walk out into the kind main hallway that we have and the lights were still on. >> reporter: the lights he'd left on when he went to bed. which meant what? david was 17 years old. the eldest of pam zimmerman's three children. they, not uncommonly, left the lights on for their mom when she worked late at her financial planning business. or when she stepped out with her new man. typically, when she got home, she turned the lights off. but this tuesday morning -- >> her bedroom is dark, and it

looked like no one had been there. >> reporter: tell me what was going on in your mind when you saw that? >> my mind was probably in a million different places. i thought it was the weirdest thing. i was like, "all right, she didn't come home, so where is she?" >> reporter: had to be a reasonable explanation. pam zimmerman was so reliable. two years divorced, a successful businesswoman and fully engaged mother. a pillar of the neighborhood. david and his 15-year-old twin sisters, heidi and rachel, tried to push their worries aside. >> we made up like every possible excuse there could've been for why she wasn't coming home. >> you don't want to focus on that. >> yeah. >> reporter: but some signs were hard to ignore. for one thing, the night before, when pam didn't respond to her kids' text messages, heidi tried tracing her, but what she found didn't make sense. >> my mom and i shared a, like, find my iphone account, so i looked it up on her computer, where her iphone was. and i saw it was in this -- it wasn't at her office.

it was in a weird location. i convinced myself that she was at a client's house, because that was my excuse at the time for why she wasn't home. >> reporter: still, their mom was a rock. center of their universe. they told themselves they'd be laughing about this later, or they'd be relieved, anyway. >> we said, "let's just get ready for school." just keep on with our day. >> reporter: she'll be home when we get home. >> yeah. >> reporter: same time. same morning. and just two doors down the street, one of pam's closest friends, julie koh, was still in her pajamas. >> my home phone rang, which is odd, because your home phone never rings that early. >> reporter: it hardly ever rings ever anyway. >> right, right. i mean, we're, i know, one of the rare people that still have a home phone. and so i picked it up and it was scott. >> reporter: scott baldwin was pam zimmerman's fiance. he lived a few hours away, near chicago. >> he said, "i haven't heard from pam, i'm really worried. i don't know what's going on. i've been trying to reach her since last night, she's not answering."

>> reporter: so she lived just a couple houses down here, right? >> right. she's two houses down that way. so i walked down here and knocked on the front door, and david answered. i said, "where's your mom?" and he said, "i don't know. she didn't come home last night." and i said, "what do you mean she didn't come home last night?" and i said, "well, where is she?" i believe they had been trying to reach her since 5:30. the night before. >> reporter: and nothing. >> and she didn't answer. >> reporter: for the kids, she tried to hide the worry flooding into her brain. >> she's like, "okay, just go to school like you normally would and i'll text you later when i know something." >> reporter: maybe, thought julie, maybe there was some simple explanation. she rushed home, got dressed, jumped in her car and headed straight to pam's office. maybe pam fell asleep while working late. >> i don't really know. i don't really know what my thinking was. >> reporter: pam's kids tried to concentrate on schoolwork.

couldn't. >> i just remember going to school, and rachel and i sat across from two of our friends at school, and i just lost it and started bawling. the whole morning was really hard. >> reporter: by now there was a tribe of frightened people. this is pam's cousin, vicki. >> i have a brother who's 18 years younger than me. he called and he said, "they can't find pam." and i go, "what?" he goes, "they can't find pam." and i said, "that's not good." and he goes, "no it's not." >> reporter: the drive to pam's office didn't take long. julie koe pulled into the parking lot. and right away, she saw something that would lead her to call 911. when we come back -- an awful discovery at pam's office. >> the lights were all off and the blinds were all pulled. >> all of a sudden i hear her say "oh my god, oh my god, oh my

god." i remember thinking, everything has changed in my life right now. everything has changed for those kids. >> there's david, and his cheeks are stained with tears. >> when "dateline" continues. when eye allergens attack, the itch can last 24 hours. but with pataday once daily relief extra strength you get fast, 24-hour relief in one drop. make it a pataday with the drop that's right for you. now without a prescription. everywhere. nexgard is the flea and tick protection

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november 4th, 2014. julie koe, full of trepidation, arrived outside the business office of her missing friend and neighbor pam zimmerman. nobody around. except wasn't that pam's car in the lot? julie called her husband. >> and he said, "call 911." so i called 911. and she said, "do you want to file a missing persons report?" and i said, "i don't even know if she's missing." >> reporter: and then she saw someone who could help. >> right as i pulled in, ina was parked right over there and she was getting out of her car and walking towards me. and -- >> reporter: and you knew ina well. >> and i knew ina. right. so i jumped out of my car and i said, "pam didn't come home last night." >> reporter: ina hess was pam's friend and longtime office manager. ina said pam seemed fine the day before. said when she left, around 4:30 p.m., pam was meeting with her last client of the day behind closed doors. but ina had a key to the building and office, so the two women headed in. >> i opened the door there and

the lights were all off and blinds were all pulled. >> reporter: was that unusual? >> very. the blinds in my area, the reception area, were never closed. >> reporter: but they were this time? >> they were closed. and i reached over and turned the light switch on. >> all of a sudden i hear her say, "oh my god, oh my god, oh my god." and i walked over to where she was, and we could see pam's body kind of laying in a fetal position. >> reporter: julie is a nurse. she checked for signs of life. >> i remember leaning down and, you know, checking for a carotid pulse. and i remember thinking, "everything has changed in my life right now. everything has changed for those kids. and their life will never be the same." >> reporter: so, there are two things going on at once there. >> right, right, that's how you're trained. you immediately focus, emotions are put aside. i knew something was bad. i knew something wasn't right.

i knew not to move her. >> reporter: ina hess stared, rooted to the spot. >> i guess i kind of went into shock, because i just -- i saw her lying there. >> reporter: but you had no idea what had happened. >> no. >> reporter: like she could have had a heart attack or something. >> could have. >> reporter: or maybe she tripped over a footrest behind the reception desk. >> kind of in the back of my mind, i'm like, "well, did she hit her head?" >> reporter: police arrived in minutes. julie's phone still pinging. >> the kids are still texting, i keep saying, "someone needs to go to them and tell them what's going on." >> reporter: eventually, officers went to the high school. one by one, pam's children were called to a conference room, where the police told them their mother was dead. >> that was the worst part, that they didn't tell us all together. they brought me into this room, and there's david, and his -- and his cheeks are stained with tears. and i just had to see that. and then they told me, and then i was just bawling, and then david starts bawling again. >> and then like half an hour later, the same thing happens

with rachel. >> reporter: oh, lord. i can't imagine a day like that. did you know where your dad was? did you know where any sort of center of your lives was? >> no. >> we didn't know anything after that. they just took us into questioning. >> reporter: but then, it was hard for anyone to focus on anything other than loss. all-consuming grief. >> she was the neatest friend, cousin, you could ever ask for. you needed something, she'd be there in a heartbeat. >> reporter: outgoing, gregarious type? >> oh. she would talk to anybody. everybody knew her. >> and she made everybody feel like they were, you know, one of her closest friends. that's how she was. and she was sincere. >> reporter: a caregiver. yes, that was pam zimmerman. but to her sister, diane gifford and brother, larry alexander, pam was also the family's smart, ambitious star. >> she was valedictorian of her

class, graduating class. >> she was a straight a student her entire grade school and high school, except i think one "b," which she got in home-ec. >> i mean i've always known we had the most amazing mom. such a bright happy person. full of wisdom, smart, funny. i could go on and on. >> she always made sure that we came first. she'd come home from work, she'd make us dinner, she'd stay up all night helping us with homework or doing our laundry. >> we called her, like, supermom because she literally did everything. >> reporter: and yet for all the love she inspired, pam zimmerman must have stirred something dark in someone or got in someone's way. wasn't long before the police figured out that her death was no accident. what did the police tell you? >> nothing. they kept the evidence very, very, very quiet.

>> reporter: when did you find out how she was killed? >> a few days later, police called me and said that the newspaper is going to release some information. you should tell the kids." and the only thing they would tell me is the cause of death was multiple gunshots. >> reporter: pam zimmerman had been murdered, but by whom? coming up -- police start with the men around her. her new fiancé. >> he had at least two other women that he had been involved with. >> her final client. >> he owned a .9-millimeter gun. >> reporter: and she was shot with one of those. >> and what about her ex? when "dateline" continues. i'm morgan, and there's more to me than hiv. more love,... more adventure,...

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>> reporter: there was no doubt. pamela zimmerman was the victim of cold-blooded murder. happened sometime before midnight. was the coroner's best guess. the murder weapon, a .9-millimeter handgun. >> there were two bullet wounds in her chest, in the front of her body. >> reporter: edith brady-lunny is a longtime pantagraph crime reporter. >> there was one bullet wound in her temple. and then there was one bullet wound in her back. >> reporter: so, somebody making absolutely sure she was good and dead. >> exactly.

>> reporter: what was that like to hear that, that news? >> it was -- the worst phone call of my life. to think that -- someone shot her and just let her die. >> reporter: and pam's kids, when they heard that? >> i always told myself she didn't see it coming, just because that was the easiest way for me to cope with it. >> reporter: an execution, is what it looked like. or maybe an office invasion robbery? didn't seem likely, but -- >> they wanted to do a walkthrough to see what was missing or what was out of place. >> reporter: did you notice anything wrong, anything missing? >> the phone cords had been cut and the phones were gone. and my calendar that i kept all of her appointments on, that was gone. >> reporter: pam's purse was sitting on her desk, gaping open. her wallet was gone, cell phone, too. its case was lying on the floor.

did you get the sense that maybe the police thought somebody wanted to steal something and they were in the process of it and got interrupted or something? >> they could have thought that. >> reporter: but there was no sign of forced entry. none. and cops found pam's cell phone right where her daughter's find my iphone account said it would be, her wallet close by, with her credit cards all there. >> so the police believed early on that this was a staged effort to make it look like it was a robbery. >> reporter: but who'd want to kill pam and then stage some strange half-hearted coverup? start close is the old adage. which meant, in pam's world, on that day, three men. her last client, that last day of her life. her ex-husband. and her brand-new fiance, scott baldwin, the object of a whirlwind romance and, perhaps,

a too-rapid engagement? after all, no one in the family really knew him. not even her kids. >> i had only met scott three times, and the third time was the party that they had to celebrate their engagement. >> reporter: that celebration was just days before, yet when scott heard about the murder, he did not rush to bloomington from his home just two or three hours away near chicago. >> it just made me realize and think what my mom really meant to him, what we really meant to him. he sounded fake at that point. >> reporter: pam's kids had questions about scott. and so did detectives. >> he was asked to come down to bloomington to meet with police, which he did the following day, after pam's body was discovered. >> reporter: scott told the detectives he'd been home alone when pam was killed. police would look into that, but in the meantime they discovered something very interesting about pam's new fiance.

>> they spent a fair amount of time checking into who he had been communicating with. >> reporter: sure. >> and he had at least two other women that he had been involved with that he was still having some pretty heavy amount of contact with. >> reporter: pam's kids didn't know anything about that, but they did get a weird vibe from the fiance after their mother's death. >> he was like, "i had nothing to do with this. and i need you guys to understand that, like, i have to move on." >> reporter: i'm sorry, repeat that for me? >> we had dinner with him like a week after she died, and he sat us down. >> reporter: did you ask him if he had something to do with it? >> no, he just volunteered that. >> reporter: and two months later, he was dating someone new. >> it was just very suspicious. >> reporter: but pam's daughter rachel thought it was much more likely her mom's murder was somehow tied to her business. she was an accountant and financial advisor.

>> maybe she found out something that one of her clients shouldn't have been doing. and this client would've lost a lot of money. >> reporter: ina hess told the investigators that pam's last client, day she was murdered, was a man named eldon whitlow. did he have any beefs with pam? >> there was no evidence that eldon had any beefs. they had a long-term, professional relationship where she was helping him with his investments. >> reporter: whitlow told detectives his meeting with pam was uneventful. he left around 5:40 p.m., he said, then had dinner with his girlfriend. he was cooperative. but -- >> he owned a .9-millimeter gun. >> reporter: and she was shot with one of those. >> that matched the type of gun that she was killed with. >> reporter: now that was a development. >> eldon whitlow was considered a person of interest. >> reporter: detectives got a search warrant, and eldon turned over a .9-millimeter. the .9-millimeter? they sent it off for testing.

and as they waited for the results, they drilled down on that one more possible person of interest. the third man. a man who just might have had a motive. pam's ex-husband, kirk zimmerman. look at him, said pam's family. there was something going on there. >> problems. >> it definitely turned into hatred. >> a lot of problems. >> reporter: problems? hatred? exactly what was the problem between pam zimmerman and her ex-husband kirk? coming up -- the ex, the client, the fiance. revelations about them all. >> reporter: who was it who said, no secrets in a murder investigation? >> exactly. >> when "dateline" continues. tis f flavor is #1 with dogs. ask your vet about nexgard.

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install a new leadership team to manage its vac vaccine producti. this comes off johnson & johnson announced wednesday that a batch of its key vaccine ingredient didn't meet quality control standards at the baltimore facility. the doses available to the public were made at a separate facility authorized by the food and drug administration and were not affected by the issue. now back to "dateline." welcome back to "dateline." financial adviser pam zimmerman had been gunned down in her office. detectives wondered if the motive was professional or personal. digging deeper, they discovered that each of the men under investigation had something to hide and one in particular was withholding crucial information about the night pam was killed. here again is keith morrison

with "before midnight." >> reporter: police investigating the murder of pam zimmerman now had a short list. her fiance, scott, her client, eldon, and a third man, her ex-husband kirk. some of pam's relatives were convinced, though, that kirk should have been the first, maybe only name on that list. >> she would always say that if anything ever happened to her, he should be the person that we should look at. >> reporter: i mean, you kind of wonder when she said a thing like that. >> well, and you wonder and you think, "oh, come on. you don't really mean that." >> reporter: did you say that to her? >> yeah, and she goes, "oh no, vicki, i mean it." >> reporter: so in the hours after his ex-wife's murder, kirk zimmerman spent a lot of time with detectives. and he answered their questions calmly. >> and you work for state farm sir? >> yep. >> reporter: not once did he ask for an attorney? >> what do you do for state farm? >> i'm a systems analyst.

>> reporter: when they asked about the divorce, kirk said his only real concern was for the kids. >> i would have preferred to keep going, at least until the kids were off to college. because by then, they're adults. >> reporter: the detectives asked kirk what he did the evening pam was killed. he said he was at home, started to read, must have dozed off. >> i have noticed lately when i read i tend to fall asleep. >> reporter: nothing, not even this, seemed to rattle kirk. >> did you murder your wife? >> no. >> reporter: they got his fingerprints, and a dna sample, and they did a gunshot residue test. >> am i required to do this? >> reporter: he wasn't, but he did it anyway. and he didn't resist handing over his phone, or his laptop, or passwords either. his car and house were another matter, though. police had search warrants for those. >> he was dropped off at a hotel. >> reporter: because he didn't have his house anymore.

>> because he did not have a house. the police were there, and stayed there for six days. >> reporter: wow. >> yeah. >> reporter: no discoveries, really. except, kirk had a girlfriend named kate, and she revealed something very curious. she and kirk had a date scheduled the night pam died. kate arrived early to kirk's house, around 6:30. rang the doorbell. no answer. well, well, well. kirk hadn't told them about any date. and certainly hadn't revealed he didn't answer the door when she rang. so, second interview. they pressed him again. >> what was the reason why you didn't say that kate was around? >> uh, i love her and just keep her out of this. >> reporter: still, the girlfriend's story put a hole in his alibi. was he home the night pam was killed, or was he somewhere else?

>> well, it was one that the police really had to sort through to see. >> reporter: sure. >> if it was a credible story or not. >> reporter: they let him go, again. kirk's kids couldn't see their dad as a suspect. they said their parents' divorce had been drama-free. >> i think they both realized that they came to want different things. >> reporter: kirk's brother, zim, agreed. he was pam's best friend and he loved her like a sister, saw her marriage up close, and the way it ended. >> there was never any hostility, open-air arguments. the kids and i, we -- we never saw anything. >> reporter: if anything, they said, the two seemed much happier. kirk got a house just down the street and around the corner. just to be close to them. >> i'm really glad he did. it made it really easy on us. >> reporter: and he did stay very involved in their lives.

>> dad videotaped all of our sporting events. a lot of soccer games, a lot of basketball games, softball games. >> reporter: besides, their dad now had kate. they'd been dating for more than a year. >> i really liked her. >> yeah, kate's awesome. >> yeah. >> reporter: so, dad, a murderer? seemed absurd to the kids. >> i think he was happy with where he was at. >> reporter: now days, months slid by. the detectives were busy, but very quiet about it. while everyone waited, they tested that .9-millimeter turned in by pam's client, eldon whitlow. >> it was not the gun that had fired the bullets that killed pam zimmerman. >> reporter: they checked his alibi, discovered he did have dinner with his girlfriend, and later that evening he met another woman. >> he had been checked out, and then he had been cleared. >> reporter: as for the fiance, scott baldwin, his secret dalliances raised eyebrows, but

wound up working for him. police confirmed he had been miles away when his fiance died, phoning and texting two other women. >> reporter: what is it about the men in this story? >> both of the men had to make some pretty embarrassing admissions. >> reporter: who was it who said -- maybe it was agatha christie. no secrets in a murder investigation. >> exactly. they both had to admit that they had been messing around. >> reporter: but kirk? not so easy to clear him. so police followed the money, and they heard things, different things from what his kids and brother said about the divorce. like a simmering resentment that pam got the house after the divorce, and most important, more money from him. >> he had a goal of retiring at 55 from very early on, in his 20s. >> and it got all messed up. >> reporter: the dispute of the moment? days before she was killed, pam

fed-exed kirk a demand, pay close to $4,000 in expenses for the kids, or else. >> she was giving him five days to pay it or she was going to take him back to court. >> reporter: office manager ina said pam told her she was truly afraid of kirk. >> i just warned her that when she worked late at night, make sure she went out the front door where all the lights were on, and make sure that she was, you know, always cautious. >> reporter: money. the root of all evil? and something else they found. what was that telltale residue in kirk's car? it was enough. on a summer morning, eight months after pam zimmerman's death, a cop turned on his squad car lights and sirens, pulled over a motorist, read him his rights. kirk zimmerman was under arrest for murder. coming up -- >> greed. hate. murder. >> reporter: prosecutors lay out

their case with a dramatic eyewitness. >> that man sitting over there. >> she saw a guy coming out that back door of pam's office. >> when "dateline" continues. before voltaren arthritis pain gel, my husband would have been on the sidelines. but not anymore! an alternative to pills voltaren is the first full prescription strength non-steroidal anti-inflammatory gel to target pain directly at the source for powerful arthritis pain relief. voltaren. the joy of movement.

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it was july 21st, 2015. the kids were now living in their dad's house. >> we woke up to the doorbell ringing. and so i go down. i open the door, and he's like -- introduces himself as a detective. and he's like, "we just arrested your dad." >> reporter: and just like that, a second parent was gone. the twins, still minors, were told they'd be living with pam's siblings now. >> rachel and i were taken into dcfs custody, where we were forced to live with them for three months, in our mom's house. so that was just -- one huge nightmare. >> it got to be hateful, angry, all the time, no matter what we did. >> reporter: but of course, pam's kids knew perfectly well that their aunts and uncles believed their dad killed their mom. >> i was 16, and our aunt diane sat me down alone in my mom's

family room and she just plainly said, "your dad killed your mom." >> reporter: what do you think about the possibility that your dad could be violent like that? >> no. i know anyone's capable of doing anything, but we would know. we're his kids. we lived with him. >> i honestly believe if she ever really felt threatened, she really felt at risk, the first person she would have reached out to was me. and she never did. >> reporter: kirk spent four months in jail before bonding out. and for the next three and a half years remained under house arrest. >> he couldn't leave the house. rachel and heidi couldn't stay in the house with him alone. there had to be another person who was 18 or older the entire time. >> reporter: the whole time, waiting for trial? >> uh-huh. >> up until we turned 18. >> reporter: until you turned 18? >> yeah. >> reporter: pam's neighbor and friend, julie koh, tried to help. >> i took his daughter driving, because they were learning to drive.

i remember driving one daughter to college. she went to mizzou, so i took her. >> reporter: but while friends tried to help pam's kids, they could not protect them from a widespread and very public suspicion that their father killed their mother. and the case always seemed to be in the news. >> potential evidence that came out was pretty damaging to kirk zimmerman. because a lot of it dealt with the exchanges he had with pam during the divorce. >> reporter: those exchanges were front and center when the state finally presented its case at trial. >> greed, hate, murder. >> reporter: assistant state's attorney brad rigdon told the jury the motive was clear. kirk zimmerman killed his wife over money. >> he knew that as long as she was still alive, he was going to go to broke.

>> reporter: the motive and the means, said the state. kirk's cell phone put him at home the night his ex died. but the prosecutor told the jury that kirk's car, a hyundai, told a different story. the car, like most cars now, had an onboard computer, a kind of gps device. and an fbi analyst said that device revealed that the car was in the vicinity of pam's office. so -- >> the police got some surveillance video pretty early on from a building nearby pam's office. and they believe there was a car that matched kirk zimmerman's. >> reporter: and, said the prosecutor, there was an eyewitness. this woman. so nervous as she took the stand she could barely get her name out. >> spell your first name.

>> m -- >> reporter: but what she had to say was important, said pam's brother. >> you know, she saw a guy coming out that back door of pam's office. she didn't know that was pam's office at the time. >> reporter: and that man, she said, was carrying a bag. what did he do with the bag? >> put it in his car. >> that was the stuff he took out of the office. >> reporter: and who was that man? on this point, the state's emotional witness was certain. >> that man sitting over there. that man sitting over there. >> reporter: investigators never found the murder weapon. but on the gearshift in kirk's car, gunshot residue, said this forensic scientist. >> that gearshift handle either contacted a gunshot residue related item, or was in the environment of a discharged firearm. >> reporter: but remember the friends and family who said pam

told them she was afraid kirk might kill her? that was hearsay, ruled the judge. >> they were not allowed to present that to the jury. >> reporter: you know, in a case where they're alleging that an angry ex-husband killed his wife, motive is everything, frankly. >> yes. >> reporter: the jury did hear all about that letter pam fed-ex'd to kirk days before her murder, demanding $4,000. pam's ongoing financial disputes, said the prosecutor, were going to prevent kirk from realizing his cherished dream of retiring early. and he wasn't going to take it. so he killed her. >> the receipt of that october 24th letter was the triggering event that culminated in the murder of pam zimmerman. >> reporter: to which pam's children replied, "ridiculous." >> i didn't think it made any sense at all. >> reporter: the defense was up next with its own case.

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welcome back. kirk zimmerman was on trial for the murder of his ex-wife, pam. the prosecution argued gps technology put his car near the crime scene and gunshot residue was found inside the vehicle. but the defense was ready to tackle that evidence head-on and raise troubling questions about the investigation. the courtroom was divided. and the verdict was about to fracture a family. back now to keith morrison with the conclusion of "before midnight." >> reporter: there were so many little pieces. so many bits of evidence to parade before the jury. the case against kirk zimmerman went on for more than four weeks, through 40 witnesses. and pretty much all of it, said pam and kirk's children, was wrong. >> you can put together little pieces any way you want. but the way they put it together wasn't the right away.

>> reporter: so now, bloomington would hear kirk zimmerman's side of the story. >> kirk zimmerman did not shoot and kill pamela zimmerman. he didn't shoot and kill the mother of his three children over owing $3,900 in child support. >> reporter: that state theory that kirk killed pam over money? nonsense, said his defense attorney john rogers. kirk made it clear to police, he said. that fedex from pam was no big deal. >> it didn't affect me. you're wondering if i disagreed or argued with her about it? >> kirk had a full pension guaranteed for life which he could have taken at any point in time. he was making $95,000 working for state farm. he had in excess of $240,000 in his 401(k). >> reporter: the defense told the court that police had tunnel vision from the very start. >> it's the old, "let's go look

at the ex-husband. he must've done it." >> reporter: that grainy video the prosecution suggested was kirk's silver hyndai sonata? really, said the defense? how could you tell? >> i don't remember the month and the year. i don't! and i don't want to hear no more! >> reporter: then there's maria legg, the prosecution's only eyewitness. >> i had a very difficult cross-examination with her. because she simply chose not to respond to me. >> i don't want to answer to you because i'm going to say what i saw. >> reporter: and when she did respond, her testimony contradicted the prosecution's evidence. like, for example, the color of kirk's car. >> you said during direct examination that it was a black car that this gentleman went to with the big bag, correct? >> yes sir. >> all right, that's not a silver car, is it? >> i saw black. that's it. >> reporter: the defense also challenged that data taken from

the onboard computer system in kirk's silver hyundai, pings the state said put the car near pam's office. the defense called it junk science. >> this type of expert testimony has never been allowed in the state of illinois before. it should not have been allowed in this case. >> reporter: but how could the defense answer for that gunshot residue found on kirk's gearshift? a defense expert agreed, there was plenty of it on that spot. but -- >> finding that number of characteristic of gunshot residue particles is surprising. >> reporter: maybe too surprising? especially because there was none anywhere else in the car. so it looked like some kind of mistake or worse. your suggestion is, what, that -- >> either gunshot residue was purposely placed on the lever or came into contact with either

clothing, a firearm, or the hands of the two police officers that had been in the crime scene. >> reporter: either way, rogers suggested sloppy police work was the hallmark of the investigation. he said police should have dug deeper when they heard what this woman had to say. >> i heard what i believed to be gunshots. >> reporter: the defense had an earwitness of sorts who testified that, though more than a block away, she heard gunshots at the office at 5:10 p.m. which fit the coroner's time of death window of sometime before midnight. and why was that important? >> that's the exact time that mr. whitlow has himself in pam's office. >> reporter: eldon whitlow, pam's last client of the day. >> i'm not contending that i had enough evidence to prove mr. whitlow shot pam zimmerman. but certainly when they claimed that they investigated mr. whitlow with the same intensity that they investigated

mr. zimmerman, that was not true. >> reporter: but police said they investigated whitlow thoroughly and cleared him. the lawyers made their final appeal to the jury. >> this is not what proof beyond a reasonable doubt looks like. we do not speculate people to murder convictions. >> the evidence has shown you that on november 3rd, 2014, he murdered pam zimmerman. and he made sure his hate got carried out in that fourth shot. that one was for him. find the defendant guilty. >> reporter: the family, as polarized as the most poisonous politics, waited. >> i was just pacing back and forth, kind of freaking out a little bit. >> reporter: and then after a day and a half of deliberations, the signal, verdict. >> welcome back, ladies and gentlemen. everyone may be seated. >> i was shaking. it just felt very long.

>> reporter: the courtroom was utterly silent, a collective holding of breath. >> we the jury find the defendant, kirk zimmerman, not guilty of first degree murder. >> reporter: not guilty. the children exhaled. >> it was just this huge relief just to know that our dad wouldn't be going away for something he didn't do. >> we just cried and smiled. it was the best feeling ever. >> across the aisle was a different world. >> i remember saying, "no." >> yeah. >> then they took us upstairs to the state's attorney's office. >> the state was just as devastated as we were. >> reporter: are you used to this yet? >> no. >> reporter: not been very long. >> no. there's still a lot of anger. >> there's nothing you can do now, right? >> no, there's not. >> reporter: a family truly divided. diane and larry, angry, disappointed. their nieces and nephew, elated

and hopeful. >> my dad can actually go out to eat now. so we've been going out to restaurants. he came with me to my dentist appointment. because he hasn't been able to do that in a really long time. it's kind of awkward, because i'm 20, but -- >> he's just trying to make up for the lost four and a half years. >> reporter: now, said david, rachel and heidi, they're hoping the state will solve their mom's murder. >> i obviously hope that they do catch whoever did it. but i wouldn't be surprised if they don't. >> reporter: what's going to happen to the family? >> i think all of us want to move out of bloomington. >> yeah. >> that's for sure. >> reporter: something else. after all the trauma, these three are, by the look of it, fine. it's because, they said, they had a wonderful mother. pam zimmerman. you three have all done pretty well so far. what would she think about where you are in life and what you've accomplished?

>> i think she'd be incredibly proud of how well we've handled everything and how it hasn't, like, derailed us. >> you think about what -- how she would want you to live and how she would want you to keep going. so that's what i've just been trying to do. keep going. so, what's what i have just been trying to do. >> that's all for this edition of "dateline." i'm natalie morales. thank you for watching. i'm craig melvin. >> and i'm natalie morales. >> and this is "dateline." i refuse to live in fear. >> you're dead. >> ever since i heard it, it's been replaying in my head, over and over. it was, all, very unbelievable. >> reporter: it