ST. LOUIS — One of two teenagers who pleaded guilty in the shooting death of a retired St. Louis police sergeant is asking to withdraw his plea.

Jalynn Garner, 17, contends in a court motion that he was pressured into pleading guilty to first-degree murder and other charges in the October 2018 death of retired Sgt. Ralph Harper, The St. Louis Post-Dispatch reported.

Garner also contends in his motion that prosecutors reneged on an agreement to allow him to plead guilty to reduced charges.

Authorities say Garner, who was 16 at the time, and Justin Mathews, who was 15 shot Harper after trying to rob him. The teenagers were certified to stand trials as adults.

As part of Garner's plea, Circuit Judge Clinton Wright ordered him to be screened for program that allows juveniles to be eligible for parole at age 21. But youth services told Garner he wasn't eligible for the program. Because of that rejection, the only possible sentence for Garner in a first-degree murder case are life with parole, or 30 to 40 years.

A hearing on the motion was scheduled for Dec. 19.