Sergeant Khamtahn Stanley has been suspended but it is not known what role, if any, he played, the Samoa Observer reports.
Police Commissioner, Fuiavailiili Egon Keil, confirmed the suspension but declined to provide any further comment.
Penitito Toma, died on Sunday night at the Tupua Tamasese Hospital, after allegedly suffering a beating.
Police say alcohol is suspected to have been a contributing factor.
Mr Stanley has prosecuted a number of high-profile cases during his career including being involved in the recent inquest into the death of two infants following the incorrect administration of a vaccine last year.
He has also been recognised as part of a multinational peacekeeping force in South Sudan in 2014.