Investigators said at a news conference Alex Anthony Madrid's DNA matched that found on the body of Claudia Lucero, KNXV-TV reported. Madrid was arrested Friday on a probation violation charge.
Mesa Police Chief Frank Milstead said Madrid had been living with Claudia's mother but moved out after he allegedly touched the teenager inappropriately.
Claudia's body was found in a garbage container just after midnight Friday but was not positively identified until Monday. Her family last saw her early Thursday.
Claudia was sexually assaulted and strangled, Milstead said.
Madrid faces a long list of charges, including first-degree murder, kidnapping and sexually abusing a child, police said.
A candlelight vigil was held Monday night at the place where the body was found. Relatives describe Claudia as a bright and active high school freshman.