WETASKIWIN, Alta. -- A judge has convicted a drunk driver of manslaughter for killing three young men when his pickup truck with its gas pedal to the floor plowed through their car at 199 km/h.

Court heard Jonathan Pratt had a blood alcohol level nearly three times the legal limit when rescue crews found him underneath his mangled Dodge Ram near Beaumont, just southeast of Edmonton, in November 2011.

The only other people at the scene were the three victims -- crushed to death in their demolished Pontiac Grand Am.

Manslaughter is a rare conviction in a drunk-driving case. But Crown prosecutor Ryan Pollard said the stark facts called for the charges, even though there have been less than a dozen convictions in past cases involving deadly crashes across the country.

Pratt's lawyer had argued that his client hadn't been driving that night, but the defence didn't call any witnesses, not even Pratt, to say who might have been behind the wheel.

Queen's Bench Justice Paul Belzil ruled it would have been "practically impossible" for a mystery driver to walk away unharmed from the "catastrophic collision." Pratt, 30, suffered a broken leg and head injury and spent the next six weeks in hospital.

Court heard there were no footprints in the snow at the crash site. And although unidentified DNA was located on a passenger airbag in the truck, Pratt's DNA was on most of the other airbags in the vehicle, including the one on the driver's side.

Pratt was also convicted of impaired driving causing death. But the judge determined he was also guilty of the more serious offence of manslaughter for showing "wanton and reckless disregard" for the safety of other people on the road where the posted speed limit was 70 km/h.

Evidence showed the truck's pedal was fully depressed. The vehicle didn't swerve and didn't brake to avoid the car in front of it.

Sheri Arsenault said she was a bit stunned when she heard the verdict. Her only son, 18-year-old Bradley, had been on his way home from a lounge in nearby Leduc with his close friends Kole Novak, also 18, and Thaddeus Lake, 22.

"The judge absolutely said every single thing that we wanted to hear," she said outside court Thursday. "I think for a second there, I was happy. And it's one of the first times I've been happy in a long time."

Court heard either Arsenault or Lake had been driving the car. Toxicology tests showed Arsenault had some marijuana and a small amount of alcohol in his system and Lake was too drunk to drive. But the judge said those facts were irrelevant.

The car was going the posted speed limit, Belzil noted, and the three did nothing to cause their deaths.

Prosecutor Gordon Hatch said he may argue that Pratt should serve eight to 10 years. Sentencing arguments are to be heard Aug. 1.

Sheri Arsenault said no prison term can bring back her son, but she has met twice with federal Justice Minister Peter MacKay to discuss possible changes to Canada's impaired driving legislation.

Arsenault is a spokeswoman for a group called Families for Justice, which is collecting names on a petition demanding a mandatory minimum sentence of five years for convictions of impaired driving causing death. The petition also calls for the Criminal Code to redefine the offence as vehicular manslaughter.

Zane Novak, Kole's father, said he'd like the federal government to go even further and change the law to allow consecutive instead of concurrent sentences in drunk-driving cases.

"These three boys died and I think there should be sentences of 10 years per boy," he said.

As he left the courthouse, Pratt swore at reporters, then briefly spoke for the first time about his sympathy for the victims and how he thinks about them every day.

"It affects every aspect of my life."

He said when he hugs his mother, he thinks "of the boys who are unable to do that with theirs."

He refused to talk about whether he was driving the night of the crash. He said the court has already decided what happened.

"That's what it says -- my DNA's all over airbags, everywhere, so there you go.

"You guys can come to your own conclusions."