A Westbury man who stabbed and threw his former roommate down a basement staircase was sentenced Tuesday to 15 years in prison, Nassau prosecutors said.

Wilson Garcia, 20, must also serve three years of post-release supervision.

A jury convicted Garcia last month of four counts of assault, four counts of robbery and criminal possession of a weapon, authorities said.

Garcia was a crack cocaine user and day laborer who once worked and lived with the 35-year-old victim, the Nassau District Attorney’s Office said.

When they were together Nov. 10, 2015 in a home in New Cassel, Garcia demanded money so he could buy cocaine, prosecutors said. The victim, who had a $100 bill, said he’d give the money left over to Garcia after making some purchases.

But Garcia pulled out a knife, stabbed his roommate in his right temple, threw him down the stairs, then snatched the bill out of the victim’s pocket, prosecutors said.

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“This defendant robbed and brutally stabbed his former roommate in the head and left him for dead,” District Attorney Madeline Singas said in a statement.

Despite a severed artery, the victim crawled up from the bottom of the staircase and made it across the street, where a Good Samaritan called 911, authorities said. He was taken to Nassau University Medical Center and has recovered, prosecutors said.

Garcia’s attorney could not be immediately reached Tuesday night.