DETROIT (AP) — Two teenagers who authorities say beat the grandmother of one of them to death with a claw hammer because she opposed their lesbian relationship were convicted Thursday of murder.

Separate juries found Larqeta Collier, 16, and Sharon Patterson, 17, guilty in the slaying last September of Bertha Atkins. Collier also was convicted of arson for setting fire to her 64-year-old grandmother's house.

The teens were tried as adults and face a mandatory life in prison with no chance of parole when they are sentenced April 13.

The grandmother lived with her daughter and her granddaughter. The teenagers hatched the murder plot after Collier's mother told the grandmother to keep Patterson out of the house, investigators said.

After the crime, the two teenagers went to see a movie, then surrendered to police.