ROCHESTER, N.Y. — Testimony Wednesday was all about DNA evidence in the cold case murder trial of Timothy Williams, who is accused of killing a 14-year-old girl on Thanksgiving in 1984.

More witnesses for the prosecution testified Wednesday. Several forensic experts who tested the data in the case walked the court through how they gather samples, how they understand the data, and how they determine the quality of the DNA linking Williams to the murder of Wendy Jerome.

On Thanksgiving night in 1984, Wendy Jerome went to deliver a birthday card to a friend, but she never made it back to her Denver Street home. Her body was found that night outside school 33 on Webster Avenue. Police say Jerome had been brutally and violently assaulted, with her throat slashed and her teeth knocked out.

Williams had been questioned at the time of the murder, but he was not charged in the 1980s, or the 1990s, or the 2000s, or even the 2010s, due to a lack of evidence.

The jury Wednesday heard how the forensic technology available at the Monroe County crime lab changed over the years. And as it did, DNA samples for cold cases like this one were occasionally retested. The jury heard in great detail how they look at hairs, blood and semen stains to collect data, and then how they vet that dat.

As the technology got more sophisticated, so did their profile. The breakthrough came in 2020, and led to Williams’ arrest.

This is the second time for this trial. The last judge, Thomas Moran, called a mistrial due to juror misconduct in December. Some of Wednesday’s testimony was repeat testimony from that trial — but the court did hear from Monroe County crime lab employee Mara Sommer for the first time.

The final witness for the prosecution will testify Thursday morning. After that, the defense has a chance to call their witnesses. Prosecutors say they’re hoping for closing arguments to begin Thursday.