Louise Desnoyers, shown in an undated file photo in Vermont, was sentenced to 15 years in prison Wednesday for her son's drowning death. (Rob Swanson/Associated Press)

A Vermont judge has sentenced a 51-year-old Montreal woman to 15 years in prison for drowning her eight-year-old son three years ago.

Judge Michael Kupersmith issued the sentence to Louise Desnoyers in Vermont District Court in North Hero after hearing her give a lengthy statement of apology to her family, friends and the court.

Desnoyers pleaded no contest earlier this year in the death of Nicholas Desnoyers-Langlois.

Desnoyers had originally pleaded not guilty by reason of insanity.

The judge says he determined during the case that Desnoyers knew what she was doing when she drowned the boy in August 2006.

She told authorities she held her son under water so he wouldn't have to suffer through her impending breakup with his father.