A prison guard accused of involvement in the death of an Aboriginal man in custody has told a Darwin court there was no foul play surrounding the man's death.

A coronial inquest and the Royal Commission on Aboriginal Deaths in Custody found Douglas Scott hanged himself in 1985.

His wife Letty Scott is trying to prove in a civil trial that he was killed by four prison guards.

In the Northern Territory Supreme Court, Barry Medley said he helped to conduct checks of prisoners on the night Mr Scott died.

Mr Medley said he checked door locks, but never entered a cell.

He said only in emergencies, when a prisoner was sick, would a guard be allowed in a cell.

Mr Medley told the court he had not heard of anything since the death of Mr Scott to suggest foul play.

Sheet evidence

Mr Medley was also shown photos of Mr Scott with a sheet around his neck.

Mr Medley said he had never seen that type of sheet before.

He told the court each prisoner was issued with two plain, adult sheets.

The legal representative for Mrs Scott called for the defendants to supply prison sheets from 1985 to the court.

The original sheet found around Mr Scott's neck was destroyed at the morgue two decades ago.