O'FALLON, Mo. • A former O'Fallon police detective who pleaded guilty to stealing drugs from an evidence locker will be jailed for 120 days, authorities said Tuesday.

Luke A. Smyka, 37, will then be on probation for five years if he successfully completes a substance abuse treatment program while in the state corrections system's custody, the St. Charles County prosecutor's office said.

Smyka in November pleaded guilty to 19 counts of stealing a controlled substance and two counts of possession of a controlled substance. Prosecutors said all of the incidents involved prescription painkillers.

Circuit Judge Jon Cunningham on Monday effectively sentenced Smyka to seven years on the stealing charges and three years on the possession charges but suspended execution of those sentences, which would take effect if he violates probation conditions. The sentences would run consecutively.