Oct 05 2023
Innocence After Guilt Episode 5: Mixture Interpretation and Secondary Transfer
According to the National Registry of Exonerations, there have been 3,337 exonerations since 1989 accounting for more than 29,500 years lost. In our quest for justice, how do we work to eliminate wrongful convictions? What has history taught us? What role has forensic DNA played since its emergence? In this video series we delve into the role of DNA testing in the United States in post-conviction work to exonerate the innocent and reassert convictions of the guilty.
In this episode, our experts explore the increased sensitivity of instrumentation and chemistries employed for DNA analysis and how this has led to more mixture samples of two or more people. Parsing out these samples can be difficult and subjective. Recently, work has been done to make this easier for analysts and to standardize interpretation, and it is important to consider how interpretation has changed over the years and the impact this can have on previously tried cases.
Peter Valentin describes how mixture samples can be inadvertently created by how evidence is collected at a crime scene and underscores the importance of educating crime scene investigators on where samples should be taken and why.
Tiffany Roy shares how interpretation has changed over the years from frequentist statistics to Bayesian likelihood ratio statistics. Analysts have moved away from making decisions of inclusion vs exclusion to whether or not the profile supports one proposition over another where the alternative proposition is never ruled out.
Tiffany also touches on the topic of transfer and exploring how a person’s profile arrived on a piece of evidence. She cautions that the research is still on-going and drawing conclusions at this point is dangerous and could lead to a miscarriage of justice.
Illustrating this point, Tiffany discusses the case of Dayonte Resiles, who was implicated in the 2014 murder of Jill Halliburton Su, who was found stabbed to death in her bathtub by her son, Justin Su. Evidence suggested that the crime was committed by someone close to the victim and the investigation initially followed, but shifted once Resiles DNA profile was found on a broken-in glass door, a knife, and the belt used to bind Su.
Throughout the trial, Resiles maintained his innocence and received strong support from the community. Resiles had a history of burglarizing homes with multiple hits in the database, and the sheer number of cases that Resiles was involved in gave Tiffany pause. If Resiles had cased the home or had been active in that neighborhood or if investigators had worked other sites Resiles has burglarized, it was possible that small amounts of his DNA could have been transferred to items within Su’s home if absolute care had not been taken. Additionally, prosecutors purposely left out mention of Resiles’ past burglaries, which didn’t allow jurors to consider an alternative reason for why his DNA may have been found at the home. Resiles was tried twice, with the first trial ending in a mistrial and the second finding him guilty and sentencing him to life in prison.
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