The killers who gunned down a beloved high school basketball star in the stairwell of her Harlem housing project got in because of busted locks, her family claims in a lawsuit.

Tayshana “Chicken” Murphy, 18, was murdered in September 2011 amid escalating violence between gangs in the neighboring Grant and Manhattanville Houses.

Robert Cartagena, 23, and Tyshawn Brockington, 24, were each convicted in Murphy’s murder and sentenced to 25 years to life in prison.

Her family filed a suit earlier this month against a Queens company, CLC Communications, it says was responsible for fixing the locks and intercoms at the Grant Houses.

A manager for CLC Communications denied the allegations.