Crime scene investigators can recover DNA evidence from a small drop of blood on the floor, the bodily fluids exchanged during a sexual assault, or skin cells underneath the fingernails of victims who scratched their attackers. Even the surfaces of objects and clothing can hold skin cells that a person sheds simply by making contact with them.

Sometimes called “touch DNA” samples, investigators might pull this material from a hand smudge on a window or lift it from the fibers of someone’s sweater using a razor blade or a piece of tape. According to Williamson, this type of DNA evidence accounts for about 30% of Bode’s lab work, which comprises roughly 4,000 cases a year from state law enforcement, special agencies, and attorneys around the country.

Indeed, cold case units that rely heavily on DNA are springing up throughout the U.S., some of them as leaders in the field. For instance, the Denver, Colo., police department and district attorney’s office are reviewing nearly 1,000 unsolved homicide and sexual assault cases that have useable biological evidence through their Denver DNA Cold Case Project.

The Project utilizes a state- and national-level DNA databank that constantly searches for matches between the DNA profiles of convicted felons and samples related to unsolved cases. Of the 500 investigations worked so far, the database has returned more than 100 hits indicating possible suspects.

Case in point
An example of the Project in action involves a case from the mid-1990s, in which a man raped a blind and hearing-impaired woman in her apartment. “Because of her disabilities, it was virtually impossible for her to identify her attacker,” says District Attorney Mitch Morrissey, who co-founded the Cold Case Project with a Denver homicide lieutenant.

“The case went unsolved for several years until this man broke his son’s arm in a child abuse situation,” Morrissey adds. “He was sent to prison for this crime and, as a result, ended up in our DNA database.”

When his information was loaded into the system, the databank registered a match and alerted Morrissey, who used the evidence to prosecute and convict the woman’s attacker in 2004—nearly ten years after the crime.

“For me, it was one of those moments where everything fell into place,” he recalls. “Here’s a victim who couldn’t see or hear her attacker, and we were there in court getting her justice. The DNA answered the question of who committed this crime and provided justice for a woman who wasn’t able to do that for herself.”

David Cordle is confident that DNA will do the same for Donna Dustin and her family. “Since the start of our investigation in 1997, we’ve gone through five different generations of DNA testing where we retest samples using improved technology,” he says. “Because of that, we have the ability to solve this case.”