Two teenagers who beat the grandmother of one of them to death because she opposed their lesbian relationship were convicted Thursday of first-degree murder.

Two Wayne County Circuit Court juries found Larqueta Collier, 16, and Sharon Patterson, 17, guilty in the Sept. 17, 2003, death of Bertha Atkins. Collier also was convicted of arson for setting fire to her 64-year-old grandmother's house, the Wayne County Prosecutor's Office said.

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

Atkins lived with Collier and her mother, Sandra Collier. Sandra Collier had ordered her mother to keep Patterson out of the house, but the teens' desire to be together prompted them to invent a plan to kill Atkins, homicide investigator Barbara Simon testified.