A forensic firearms specialist took the stand Tuesday at Saskatoon’s Court of Queen’s Bench as the Crown wrapped up its case against Joshua Petrin.

Petrin is charged with first-degree murder in the death of 34-year-old Lorry Ann Santos, a Saskatoon mother shot and killed inside her home in the city’s Westview area Sept. 12, 2012. Police said she was gunned down by members of an Alberta gang called the White Boy Posse, who hit the wrong house.

The firearms specialist told court the bullet casings found at the scene were fired from two guns police obtained as part of their investigation into the shooting.

He was one of two witnesses who testified Tuesday. The identity of the second witness is protected under a publication ban.

Petrin’s trial began Sept. 12 — exactly four years after the killing. Other witnesses called to the stand have so far included Santos’ widower, neighbours of the mother, Petrin’s ex-girlfriend, and a man who said he acquired the guns and ammunition used in the shooting.

Three witnesses told court Petrin ordered the hit that led to Santos’ death. An alleged former member of the White Boy Posse was the intended target, the witnesses said.

Petrin was one of three men arrested after Santos’ death. The other two were found guilty in 2013 and 2014, respectively. Both were sentenced to life in prison — though one has since appealed his conviction.

Calvin To has been covering the case since the trial began last week. He was back in court Tuesday as the Crown wrapped up its case: