50-year-old Andrew Cairns, of Warminster, pleaded guilty and was sentenced Friday before a county judge in Doylestown.
Prosecutors charged Cairns with first-degree murder for his role in the Feb. 19 shootout with police that left Marie Zienkewicz dead in the crossfire.
Investigators say Cairns traded shots with police after a dispute with his girlfriend and barricaded himself in his apartment for several hours before surrendering.
Zienkewicz, who lived in the apartment below, was struck by a police bullet and later found dead.
