DOVER, N.H. – A man charged with killing a teenager during a robbery has pleaded guilty in return for his testimony against another man who is still awaiting trial.

Michael Tatum of Barrington pleaded guilty Friday to second-degree murder, in a deal with prosecutors.

The 22-year-old Tatum was one of three men charged with stabbing 18-year-old Aaron Wilkinson of Madbury last June with a machete and knife, then dumping his body in Lebanon, Maine. A medical examiner’s report found Wilkinson was stabbed 22 times.

Zachary Pinette of Springvale, Maine, pleaded guilty to second-degree murder and other charges on April 2.

Both plan to testify against 19-year-old Tristan Wolusky, who has pleaded not guilty to first- and second-degree murder and faces trial in June.