>> that letter has been more closure to me than any kind of closure that the court could co-for me. just the fact she knew where she was going and she had that kind of faith. california police had several suspects in the robbery and murder of a retired couple. unfortunately, the forensic evidence was inconclusive. ten years later, a determined forensic scientist with materials used by dentists found evidence that had previously been overlooked, and in so doing, made scientific history. bakersfield, california, known for its oil fields, wide open spaces and an aggressive crime investigation unit.

officials post pictures of their most-wanted criminals on the town's website, but they needed every trick they could think of to solve the case of clifford and alma merck, a retired couple who lived on the city's south side. >> they loved to sit out on the front porch and they had big trees out in the front and it was shady in the summertime. >> one saturday morning, the mercks' son, robert, stopped by his parents' home for a visit. he immediately noticed something was wrong. >> he found a door open at the back of the house and entered and immediately detected a foul odor. >> i backed out of the house and told my wife, i said, something is wrong here. go across the street and call the sheriff's department. >> jim christopherson was one of the first to arrive at the scene. >> the entire residence was ransacked, everything turned upside down, chairs turned upside down. anything that was in a drawer

was tipped out and spilled out on to the floor. >> when they got to the couple's bedroom, police discovered this was more than a robbery. >> clifford merck had been lying across the bed with his hands and feet bound with some sort of a cord, and he was obviously deceased. it was later determined that he had been shot in the head twice. >> nearby police found a pillow with two bullet holes. the pillow had been used to muffle the sound of the gun shots, but there were no spent shell casings in the home. >> so, whoever committed the crime probably collected those casings to hide the evidence or to throw the investigation off track. >> the search team found alma merck's body in the second bedroom. >> there was a sliding panel in this location, and as we slid it back, one could see that there

was a body placed in this closet. >> he told me that my mother, they found her in a wardrobe with a telephone cord tied around her neck and strangled. >> alma's jewelry and cliff's handguns were apparently stolen during the attack. investigators found two foreign fingerprints inside the home, one at the back door, the other on a sewing tray in the living room. in a search for suspects, a neighbor told police that he saw two men lurking around the mercks' home just a few days earlier. >> he kept an eye on them until he finally lost visual contact with them because of trees obstructing his view. and that was the last he saw of them. >> the mercks had no known enemies, and no one else in the neighborhood saw or heard anything unusual around the time of the murders. investigators hoped that either the fingerprints or some other

forensic evidence at the scene would lead them to the killer. [ aniston ] when people ask me what i'm wearing, i tell them aveeno®. [ female announcer ] aveeno® daily moisturizing lotion has active naturals® oat with five vital nutrients. [ aniston ] because beautiful skin goes with everything. aveeno®. naturally beautiful results™. av♪eno®. we do? i took the trash out. i know. and thank you so much for that. i think we should get a medicare supplement insurance plan. right now? [ male announcer ] whether you're new to medicare or not, you may know it only covers about 80% of your part b medical expenses. it's up to you to pay the difference. so think about an aarp medicare supplement insurance plan,

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at cliff merck's autopsy, the medical examiner recovered two .25-caliber bullets from his skull. coincidentally, one of cliff's .25-caliber pistols was stolen during the robbery. investigators wondered whether cliff had been murdered with his own gun. >> we had been evaluating every .25-caliber automatic seized in the area as it came in to see if the ballistics would match the .25-caliber bullets that were removed from the skull of clifford merck. >> two months later, investigators found cliff merck's gun. it was in the possession of a man, whom we'll call dan jones, at the time he was arrested on a drug charge. it was easily identifiable since cliff's initials had been carved into the handle.

>> that was cliff. he had his name on practically everything that he owned. he'd take some kind of an etcher and etch his initials on it, you know, just for identification. >> jones denied any involvement in the murder and said he bought the gun from an acquaintance, robert cowan, a man well known to law enforcement. >> he had no occupation and he supported himself by stealing, robbing houses, stealing from people outside of restaurants and that type of thing. he had a long record of robberies and use of narcotics. >> robert cowan also had a partner in crime, his brother gerald. >> the brothers were involved in criminal activity, a lot of small-time stuff, public drunk, a lot of narcotics usage, some assaults. >> forensic scientists tested cliff's gun to see if it was the

one used in his murder. the gun was test fired into a tub of water. as bullets go through the barrel, the lands and grooves which make the bullet spin leave marks on the outside of the bullet. >> they will design the barrel to have a certain direction of twists, a certain number of lands and grooves, a certain measurement for those lands and grooves, so those are intentionally put in by the manufacturer. >> surprisingly, when the bullets from cliff's gun were compared to the guns from cliff's autopsy, they did not match. investigators checked all of the local pawn shops and discovered that the cowan brothers had pawned some of alma merck's jewelry. with a search warrant, police found several other items belonging to the mercks in the cowans' possession. >> he had a wallet, he had two social security checks which he was trying to sell. he had all types of jewelry. >> but investigators did not find a .25-caliber pistol like

the one used in the murder. investigators then compared the cowans' fingerprints and those of the drug dealer with the fingers found inside the mercks' home. they were astonished to learn that none of them matched. the cowan brothers looked similar to the men seen walking near the mercks' home before the murder, but the neighbor couldn't make a positive identification. all investigators had against the cowan brothers and dan jones was possession of stolen property. >> we just got to a certain point where there was no fresh information coming in and there was still a lack of physical evidence tying the cowans to the crime scene. >> we would talk and he would say the same thing, we think it's the same people, but we don't have the proof. >> i never lost hope. i just knew in my heart that the

police would do their job and find the people that did this to mother and cliff. >> investigators confiscated every .25-caliber pistol they could find, hoping that one of them would match the murder weapon. >> i maintained those bullets in my secured work area. i never returned them to the sheriff's property room, knowing that i would one day get that firearm. >> but eventually, there were other crimes to solve, other evidence to process, and the murder of cliff and alma merck moved quietly into the unsolved file. ten years later, jim christopherson was promoted to homicide detective, but he never forgot the murder of cliff and alma merck. >> the case had always bothered me mainly because of the circumstances, the way they were murdered and just knowing that there was that element out there still walking the streets that hopefully hadn't done more

killings. >> but after a decade, the trail of the killer had turned cold. christopherson knew he needed forensic evidence to have any chance of solving the case.

ten years after clifford and alma merck's murder, investigators in bakersfield, california, were no closer to making an arrest. >> we don't know who it was or if they were somewhere in the neighborhood still. it was really scary, very scary to think that they're still out there, they're not caught. and i tell you the truth, i really didn't think they were ever going to get caught. >> shortly after jim christopherson was promoted to homicide detective, he reopened the case looking for any possible evidence that might have been overlooked. >> when i opened up the case, it was very enlightening first off. i had no idea that the initial investigators had done so much work on it. they had talked to literally hundreds of people and

interviewed hundreds of people and had obtained a lot of good information. >> cliff merck's .25-caliber handgun stolen during the robbery was recovered a few months later, but ballistic tests revealed it was not the murder weapon. in searching through the files, christopherson discovered that there were several other men present on the night the cowan brothers sold cliff merck's gun to the drug dealer. when christopherson reinterviewed them now ten years later, one of the men present recalled an interesting detail. he recalled hearing the cowan brothers tell the drug dealer that the gun they were selling had been used in a crime. >> once this drug person took possession of the gun, he put a screwdriver down the end of the barrel and reamed it out, in effect changing the rifling of the gun. >> with this information, greg leskowski took a second look down the barrel of cliff merck's gun and saw evidence of what the

informant was talking about. >> the land impressions at the very muzzle or the crown of the barrel had appeared to have been altered. it wasn't obvious at first because it's an old gun, but there was just something about the crown and the land impressions of that muzzle that were just different from the remainder of the impressions farther down the barrel. >> since only the end of the barrel had been altered, leskowski needed to find some way to examine just the portion of the barrel that was unaltered. no one in the forensic establishment could help him. >> i contacted a number of known experts about what i was

planning to do and how to do it. they all wished me good luck. and so, you know, i felt i had to, you know, i was kind of just working on my own at that time. >> but leskowski remembered using a dental casting material called mikrosil in a case where he needed to see tool marks in a piece of metal. so, he decided to try some of that by putting it down the barrel of the gun. >> it consists of two parts, a silicone rubber base and then a catalyst or hardener. and basically it comes in two tubes. so, when one squeezes a certain amount of rubber material out and then a corresponding amount of hardener out, you mix the two together, and in this particular case, we injected the cast into the barrel and let it harden. >> it took 15 minutes for the mikrosil to solidify inside the

gun. when it hardened, leskowski slowly removed the cast from the barrel. >> it literally does not adhere to the substance that it's casting. it just records its surface detail. it's like an egg on a teflon frying pan. one can see that one achieves a very true representation of the interior of the barrel, plus the fine detail. >> he cut away the portion of the barrel imprint destroyed by the screwdriver and then compared the remainder of the cast to the bullets that killed cliff merck. in an incredible turn of events, they were an exact match. this proved that clifford merck's own gun was used in his murder and that the cowan brothers had been in possession of the gun before it had been altered. even with this discovery, it still wasn't enough to prove murder. >> that was good circumstantial evidence. however, it still did not place them inside the crime scene. >> but there was one more piece of evidence about to be uncovered that would point the

finger at who killed clifford and alma merck. for the first time in the history of forensic science, a cast made of the inside of a gun was used to identify a murder weapon. the pistol used to kill cliff n] hello? oh, man. that never gets old. no, it does not. [ female announcer ] not all credit report sites are equal. experian.com members get personalized help and a real credit report. join now at experian.com with enrollment in experian credit tracker.

>> but there was one more piece of evidence about to be uncovered that would point the finger at who killed clifford and alma merck. for the first time in the history of forensic science, a cast made of the inside of a gun was used to identify a murder

weapon. the pistol used to kill cliff merck had been sold to a drug dealer by robert and gerald cowan, but for some reason, the cowans' fingerprints did not match those found at the crime scene. >> the person who attempted the comparison was then able to make a match, and he failed to have another examiner verify his conclusions. >> this was a breach of protocol. the standard operating procedure in all crime labs requires a fingerprint examiner to have someone verify his or her conclusions. so the fingerprints were resubmitted for analysis, and this time, the results were verified by a supervisor. the fingerprints found in the mecks' home matched robert cowan. >> it goes without saying that i was highly irritated and embarrassed for the department. >> i initially on the latent evidence being misread, i tend to believe that was probably a training issue.

>> it just was simply a situation where the original examiner was in over his head and couldn't handle it. >> armed with the fingerprint evidence and the ballistic test results, robert cowan was arrested and charged with two counts of first-degree murder. >> took him back to the office and i showed him where his fingerprints were definitely found inside of that house and asked him to explain that, and he just shook his head and he just kept his mouth shut and stayed silent and said he couldn't explain it. >> gerald cowan was also arrested for the murders, but he

was later released because there was no forensic evidence linking him to the crime scene. gerald cowan was later convicted of manslaughter for killing his father-in-law. he served only two years in prison for that crime before he was released on parole. prosecutors believe robert cowan was one of the men seen near the mercks' home by the neighbor. based on the forensic evidence, prosecutors say robert cowan and an accomplice broke into the mercks' home through the back door. cliff merck probably went for his gun to defend himself and robert cowan grabbed the pistol and turned it on cliff. [ shots ] the men bound his wife, alma, locked her in the closet and left her to die. robert cowan left his fingerprints on a tray found in the living room and by the back door as he left. the cowans pawned some of alma merck's jewelry, then sold the gun to a drug dealer who altered the rifling marks of the gun barrel, but it wasn't enough to

fool a forensic scientist with his new-found ability to see inside the barrel. >> something inside me says hold on to these bullets, you're going to find the firearm. and lo and behold, it happened, way down the line, almost ten years later, but time was on our side, i guess, in that manner. >> robert cowan was convicted of two counts of first-degree murder and was sentenced to death. >> when you look at what he did to this elderly couple who he had no reason to kill, he could have taken everything they had and tied them up and left them. he didn't have to shoot them. he didn't have to shove mrs. merck in a closet and close the door and let her suffer and die. i couldn't find anything good about this man. i couldn't find anything nice about him. i couldn't find any reason in the world why he should even be walking on the earth and

breathing air. >> i'm glad they convicted him. i'm glad he's where he is. and i think that he deserves everything that he's getting for what he did to my mother. >> if they would let me, i would throw the switch or whatever it takes to do. >> the merck case took ten years to solve and required both perseverance and ingenuity. the result was not only a conviction but a new forensic test now used around the world when investigators suspect there has been tampering inside a gun barrel. >> this is where forensic science works as it always borrows or steals from its neighboring sciences or methodologies, and it takes

those and uses it in a practical manner. >> i could not have won the case, i could not have gotten the death penalty without forensic science. >> i've had a long career, and it was one of the highlights of my career. e on a bitter cold night, family home went up in flames, killing one man and leaving a second person injured. a witness blamed a kerosene heat person arson was suspected. forensic science was needed to sort through the contradictions. was this an accident or cold brooded murder. the weather in jackson, georgia, is usually warm most of the year. but in january 2003, there was an unusual cold snap, with temperatures below freezing. citrus growers used kerosene heaters to save their orange crop.