Last week, EFF filed an amicus brief in State v. Alvin Davis in California, in support of Mr. Davis’s right to inspect the source code of STRMix, the forensic DNA software used at his trial. This is the most recent in a string of cases in which EFF has argued that a defendant has the right to examine DNA analysis software. Earlier this year, the courts in two of those cases, United States v. Ellis and State v. Pickett, agreed with EFF that the defendants were entitled to the source code of TrueAllele, one of STRMix’s main competitors.
Criminal defendants must be allowed to examine how DNA matching software used against them works to make sure that the software’s result is reliable. Access to the source code cannot be replaced by testimony regarding how the program should work, since there could be coding errors. This is especially true for the newest generation of forensic DNA software, like STRMix and TrueAllele, which are fraught with reliability and accuracy concerns. In fact, a prior examination of STRMix led to the discovery that there were programming errors that could have created false results in 60 cases in Queensland, Australia.
That same worry is present in this case. Although the crime itself is harrowing, the evidence is anything but conclusive. An elderly woman was sexually assaulted and murdered in her home and two witnesses described seeing a black man in his 50s on the property on the day of the murder. Dozens of people had passed through the victim’s home in the few months leading up to the murder, including Mr. Davis and another individual. Mr. Davis is an African American man who was in his 70s at the time of the murder and suffers from Parkinson’s disease. Another individual who met the witnesses’ description had a history of sex crimes including sexual assault with a foreign object.
DNA samples were taken from dozens of locations and items at the crime scene. Mr. Davis’s DNA was not found on many of those, including a cane that was allegedly used to sexually assault the victim. Traditional DNA software was not able to match Mr. Davis to the DNA sample from a shoelace that was likely used to tie up the victim—but STRMix did, and the prosecution relied heavily on the latter before the jury. The first trial against Mr. Davis, who is now in a wheelchair due to Parkinson’s, ended with a hung jury. He was convicted after a second trial and sentenced to life without parole.
Hopefully the California court will follow the rulings in Ellis and Pickett, and recognize that there is no justice in convictions based on secret evidence.