Mesa teen pleads not guilty in mother's killing

A 16-year-old Mesa boy accused of killing his mother last month has pleaded not guilty in the case.

Michael Helms is being held on suspicion of first-degree murder, concealment of a dead body and tampering with evidence.

Maricopa County prosecutors plan to try him as an adult.

Mesa police say the teen's 17-year-old friend, Christian Blakely, also is facing charges as an accomplice to the murder of Tina Helms Spencer.

He also pleaded not guilty at his arraignment Wednesday.

The teens' next court date is Dec. 26.

Spencer's body was found Oct. 26 in a backyard shed at the family's property.

Authorities believe the 36-year-old woman was struck with a frying pan and a hammer and also was choked.

Follow this story: Police: Frying pan and hammer used to murder Mesa mother