BRAMPTON -- A giggling teenaged girl coldly told a friend that she murdered her alcoholic mom by drowning her in a bathtub because it was "a lot less messy" than an initial plan to burn her in her bed, a stunned court heard yesterday.

"Only four minutes ... that's how long I held her head under the water for ... after that, she just kept convulsing and twisting in the water," the girl says on a secret police videotape, played on the first day of the sensational first-degree murder trial of the teen and her younger sister.

"All I had to do was hold her head under water ... It's a lot easier to kill a person than you think. It's a lot harder to get away with it," she said on the tape.

The girl says murdering her mom and making it look like an accident was the "best solution" she could imagine to a "horrible" life for the sisters and their 6-year-old brother.

In their opening statements to Superior Court of Ontario Justice Bruce Duncan yesterday, prosecutors Mike Cantlon and Brian McGuire said the sisters "planned" their mom's murder and then made it look like an accident.

Cantlon said the girls told witnesses that, after giving their drunken mother Tylenol 3 tablets to render her unconscious, they led her to the bathroom and placed her in the tub.

On the video, the older sister tells a male friend she told her mom to roll over, then pushed her face into the water. She said she wore rubber gloves to avoid leaving fingerprints.

She said the girls also established an alibi by timing their mom's death so they could immediately catch a bus to Square One shopping mall and meet two friends at Jack Astor's bar and grill.

Peel police did not suspect anything until a Rexdale man came forward Dec. 17, 2003. He alleged the older sister -- a family friend -- had told him of the killing a few weeks earlier.

The videotape shows she later told her friend that her mom's life was "really, really bad. It just kept going downhill and downhill and downhill ... It was really, really horrible. It was like, you're not with your mom, she's just a drunk."

When the friend asked her why she didn't tell police, she answered: "If I did, that would just destroy my life and destroy the lives of a lot of people around me."

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