PHOENIX -- A 16-year-old Mesa boy accused of killing his mother last month has pleaded not guilty in the case.
The teen is being held on suspicion of first-degree murder, concealment of a dead body and tampering with evidence.
His name is being withheld by The Associated Press because he's a juvenile.
Maricopa County prosecutors planned to try him as an adult.
Mesa police said the teen's 17-year-old friend 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 on the family's property.
Authorities believed the 36-year-old woman was struck with a frying pan and a hammer and also was choked.
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