Cold cases where DNA trapped evil killers - DNA evidence and cold murder cases: when hidden clues catch killers.
When it comes to solving a murder, DNA, fingerprints and ballistics are just the starting point for forensic experts and detectives. Here’s what investigations look like to those in the lab
Forensics can make the difference between a killer going to jail or getting away with murder. And that often means hours in the lab for experts like forensic scientist Elaine M Pagliaro of the Henry C Lee Institute of Forensic Science. “It’s important to remember that scientific evidence [also] helps to exonerate the innocent, both before and after trial,” she says.
Here, Pagliaro and criminalists from the Los Angeles Police Department reveal the secrets and science of forensic investigations – and how they all affect cold case results.
Crime scene reconstruction
“Forensic scientists cannot know every detail of what happened,” Pagliaro says. “We are not Dexter,” the blood spatter expert and serial killer in the fictional TV show of the same name. Contrary to what many believe, she notes, a reconstruction isn’t a reenactment. It’s a detailed setup that helps experts learn more about a sequence of events or answer a specific question, like where a person was standing when an altercation began or whether a particular weapon could have caused a victim’s injuries.
In his cold case investigations, Tim Marcia, an LAPD detective, turns to old murder books to determine if the original detectives relied on crime scene reconstructions. For example, if a victim’s belongings are strewn near a murder site, he checks to see if the placement of items suggests that the killer discarded them or that victim dropped them. The path of evidence can lead to telling clues.
Physical evidence
Tangible items that link a suspect to the crime scene are classified as physical evidence. Today’s technology surrounding physical evidence can offer significant help in cold cases, according to Pagliaro. “Even fingerprints that were not visible previously may be developed with some of the new techniques,” she says. In 2011, the FBI introduced its Advanced Fingerprint Identification Technology (Afit), which includes an algorithm that has helped improve the accuracy of fingerprint matches from 92% to more than 99.6%.
In the Kari Lenander murder case from 1980, Marcia plans to use the latest technology to his advantage. “I’ve just made another request to have all the fingerprints redone,” says Marcia, adding that the analysis could take six weeks to several months.
Biological evidence
Specific subsets of physical evidence that contain DNA – sources like blood, semen, hair, saliva and various tissue – are biological evidence. For cold cases, these sources can be gamechangers. The first court conviction based on DNA didn’t even come down until 1987.
Cold case DNA evidence is sometimes treated differently than in newer cases, says Pagliaro. “If the sample is degraded.
