Forensics testimony ties Ashbaugh DNA, gunshot-residue evidence to items recovered in officer-involved shooting case

Forensic scientists testified at a Bexar County hearing that laboratory analyses linked items collected from a vehicle and a pistol to defendant Tyler James Ashbaugh in San Antonio Police Department case 22108229, an officer‑involved shooting investigation.

Caitlin McCaughn, a forensic scientist in the Bexar County Criminal Investigation Laboratory’s serology and DNA section, testified that she screened items submitted under lab case number 22‑03151 to identify candidates for DNA testing. McCaughn said the lab’s serology work determined which swabs were suitable for touch‑DNA testing but that conventional serology for blood, semen or saliva was not performed on those items.

Robert Sailors, a forensic scientist and supervisor in the lab’s biology department, told the court he performed DNA analysis on swabs from vehicle surfaces and a known standard from Ashbaugh. He said the gear‑shift swab (item E12) produced DNA consistent with four contributors and that the genetic typing “is approximately 21 septillion times more likely if they had originated from Tyler James Ashbaugh and three additional people than if they originated from four unknown unrelated individuals.” Sailors said the interior driver‑door handle…