2024/11/05

Forensic Magazine, October 30, 2024: The Chimera Case: 1 Victim, 1 Suspect, 3 DNA Contributors

At ISHI35 last month, Julie Conover Sikorsky, a Forensic Scientist Supervisor at the Palm Beach County Sheriff’s Office, spoke about an unusual case she recently encountered.

During the routine processing of a sexual assault kit, the victim’s standard was discovered to be a two-person mixture.

As if DNA interpretation wasn’t challenging enough, it looked like the lab may be working on the case of a chimera. The situation forced analysts to think outside the box to ensure accuracy and transparency—and ultimately justice.

Case background

On Feb. 23, 2023, a 21-year-old woman reported being sexually battered by her ex-boyfriend in the back of her car. The victim’s father located her afterward using the Find My Friends iPhone app when he had a feeling something was wrong.

An extensive sexual assault kit was taken, with the forensic nurse noting that the victim was menstruating at the time and had bleeding from the anal cavity.

Both the victim’s sexual assault kit (SAK) and the suspect’s physical evidence recovery kit (PERK) were sent to the lab. In April, the SAK was y-screened, and male DNA was indicated on 11 samples.

In July, analysts triaged the samples based on the Y-screening results and forwarded 2 samples from the SAK and 1 sample from the PERK, as well as the suspect and victim reference standards.

This is where the complication started—the victim’s standard was discovered to be a 2-person mixture. Only 3 loci had more than 2 allelles.

“The first thing we think of is maybe it was contaminated, but the other thing we think of is maybe its related because there’s not a lot of mixture there,” said Sikorsky.

The team stopped interpretation and requested a new standard. In the meantime, they ruled out both contamination before and during lab processing.

The second standard arrived from the victim and it was the same 2-person mixture. more