PITTSBURGH — An autopsy pathologist testified Friday that the wife of a University of Pittsburgh medical researcher was given a fatal dose of cyanide, though he can’t determine how or by whom.

Dr. Todd Luckasevic’s testimony came as Allegheny County prosecutors were wrapping up their criminal homicide case against her 66-year-old husband, Dr. Robert Ferrante. Prosecutors plan to call one more witness Monday: a medical expert who will present an animation that demonstrates the poison’s effects on Ferrante’s wife, 41-year-old Dr. Autumn Klein. Earlier in the trial, jurors heard Klein on tape groaning and gasping for air as Ferrante called 911 on April 17, 2013.

That day, prosecutors contend, Ferrante laced Klein’s energy drink with cyanide he had overnighted two days earlier to his lab, where he was trying to develop a cure for Lou Gehrig’s disease.

Defense attorney William Difenderfer, foreshadowing his strategy, asked Luckasevic whether he was aware of surveillance video showing Klein entering the building that housed Ferrante’s lab and staying several minutes after work the night she fell ill. Luckasevic said he wasn’t aware Klein was near Ferrante’s lab that night.