Crown prosecutors say they cannot prove Brent Parent knew he had struck and killed a young man on a Langley road three years ago.

Parent is on trial for charges including criminal negligence and dangerous driving causing death in the March 13, 2008 incident that left 21-year-old Silas O'Brien dead.

The Crown asked the court Friday to dismiss one of two counts of failure to stop at the scene of an accident because prosecutors cannot prove the charge beyond a reasonable doubt.

When Parent took the stand in his defence in September, he described his behaviour that night as "stupid and childish," but said he didn't realize he had hit anybody with his truck.

He said he heard a bang during a confrontation with a trio of young men, but thought someone had kicked his truck or thrown something at it.

Parent testified that it wasn't until hours later when he watched a TV news report that he learned O'Brien had been killed.

Defence lawyer Vincent Michaels made his closing arguments in the trial Friday, and focused on the testimony of the two friends who were with O'Brien when he died.

"Our position is that the two main witnesses for the Crown describe the events leading up to the impact very differently," Michaels said.

O'Brien and his friends Luke Stephen and Sam Dooley were on their way to the Seattle airport to begin a Hawaiian vacation when prosecutors say they encountered Parent's truck on a rural stretch of road in Langley.

The friends testified that they were trying to pass a truck that was stopped in front of them when it sped up and started driving beside them.

They say the Ford forced their vehicle into the ditch and then took off. The friends got out of the vehicle to inspect for damage, but five minutes later, the truck returned. Stephen and Dooley testified that they waved their hands in an attempt to stop it, but it mowed O'Brien down.

The truck fled the scene, and Parent and his brother Lloyd Teneycke were stopped by police later the same day. It took nearly a year before Parent was formally charged.

Crown lawyers will present their closing arguments in the trial at a later date.

With files from CTV British Columbia's Maria Weisgarber