An internal investigation by the Falmouth Police Department concluded that a former officer violated agency policies, including drug use, interference with proceedings, and witness intimidation.
Massachusetts State Police conducted the initial criminal investigation into former Sergeant Benjamin Guthrie, who was placed on leave in February.
The internal examination of the 50-year-old Guthrie involved repeated use of marijuana and other drugs over the past year, with evidence that supported these findings.
Guthrie was also found to have tried to undermine a superior officer's investigation and made a veiled threat against a witness.
Guthrie, who retired in March, claimed the State Police investigation was due to what he termed an "erroneous" allegation of domestic violence, and that the claims against him were not substantiated.