Whether Colton Ferguson intended to pull the trigger when he killed Heather Thurier in the Edmonton Stadium LRT station nearly two years ago will be part of final arguments on Thursday.
Ferguson, 21, is on trial for first-degree murder in the 23-year-old woman's death on May 21, 2010.
Ferguson pointed the gun in Thurier's face after she insulted him, he testified earlier this week. But he says the shooting was unintentional.
On the final day of evidence on Tuesday, Ferguson's lawyer Ashok Gill asked firearms expert Alan Voth whether it was possible to pull the trigger on the sawed-off rifle without meaning to.
Voth told the court the .22 has an average trigger weight of about four pounds for that type of rifle, which is normal for a gun used for such things as target practice.
He also testified the trigger weight for firearms used by police officers is often three times as high to prevent unintentional discharge.
Even then some police agencies train their officers to keep their fingers off the trigger until ready to shoot, said Voth.
Voth told the court the gun Ferguson was holding could be unintentionally fired when Ferguson pulled the gun back as Thurrier stepped toward him.
While watching the video of the killing, Voth believed Ferguson had his finger on the trigger most of the time.
But under cross-examination Voth said Ferguson's trigger finger was partially hidden behind the trigger guard and could have been resting behind the trigger.