On the night of June 19, 1980, 29-year-old St. Louis detective Gregory J. Erson was working undercover as a decoy in the midtown area known as the Stroll. He had made several arrests during the detail. Later that night his unmarked car was found near Whittier Street and Westminster Place with him slumped over the steering wheel from a gunshot wound to the back. He was taken to City Hospital #1 and pronounced dead in the early hours of June 20.

Investigators determined the incident was a robbery that turned deadly; the attackers stole his service revolver, badge, and wallet. Ballistics testing later matched the fatal shot to his own police-issued weapon. Witness tips led police to suspects; four were initially detained and two released. The probe centered on Robert L. Baker and Leslie Lomax. Baker gave a videotaped confession admitting he shot the detective during the robbery.

Baker was ultimately convicted of capital murder at a second trial and sentenced to death; he was later killed by another inmate while incarcerated. Lomax was convicted of capital murder and sentenced to life without parole.