Three bombs, three crime scenes and one suspect.

The trial of accused letter bomber Guido Amsel heard detailed testimony Wednesday from a Winnipeg Police Service identification unit officer who described how he kept a mountain of forensic evidence from being contaminated. 

"I treat all cases as individual cases," Const. Brian Neumann testified. "This would be no different than if I had a commercial break and enter, a robbery and a sexual assault. These are separate cases. All of the exhibits are treated independently of each other." 

'I treat all cases as individual cases. This would be no different than if I had a commercial break and enter, a robbery and a sexual assault.... All of the exhibits are treated independently of each other.' - Const. Brian Neumann

Amsel, 51, has pleaded not guilty to five counts of attempted murder and several explosives offences in connection with bombs that were delivered to two law firms on River Avenue and Stradbrook Avenue, and to his ex-wife's workplace on Washington Avenue in July 2015.

A bomb enclosed in a recording device delivered to the Petersen King law firm on River Avenue exploded and seriously injured lawyer Maria Mitousis on July 3, 2015. The two other bombs were safely detonated by police.

Amsel's defence is expected to argue forensic evidence implicating him in the crimes was tainted by police contamination. 

Exhibits seized from the River Avenue scene were stored in the basement area of the major crimes unit at the former Public Safety Building, Neumann said.

"It's a secure room accessible only by members of the forensic identification section," he said. 

"When I received case evidence from the Stradbrook address and from the Washington address, these cases were all treated separately and placed in different locations where the exhibits did not intermingle," Neumann said. 

Evidence seized from Amsel's home and workplace following his arrest was stored in a lab area on the second floor of the PSB, he said. 

"I was able to secure the exhibits of Mr. Amsel on the second floor, completely separate from anything that came from the lower-level exhibits in the major crimes room."

Identification unit officers wear rubber gloves whenever handling exhibits, the officer testified.

"I use the gloves so I don't contaminate them," he said. "I don't want to be contaminated by exhibits that I touch as well, that may include chemicals and/or biologicals." 

The trial continues.