The Prince George's County state's attorney's office dropped charges yesterday against a former deputy sheriff who was accused of stealing money from the home of a couple he was directed to evict.

According to Assistant State's Attorney Robert Bonsib, the case against former deputy Dennis Brugman was dropped after evidence was uncovered that discredited the statements of a key witness. Brugman was scheduled to go on trial yesterday before Circuit Court Judge Howard Chasanow on charges of grand larceny and grand larceny after trust.

Brugman, 34, who retired on medical diability last November, was charged with pocketing between $300 and $400 belonging to a couple he was directed to evict from the Hickory Hills apartments in Suitland in 1974.

He was one of two deputies indicted in unrelated cases along with Sheriff Don Edward Ansell last October. Ansell was acquitted last month on charges that he misappropriated nearly $2,000 in funds from a sheriff's department banquet, then failed to report the money on his state income tax and lied to a grand jury about it.

Former deputy Raymond W. Barry was also indicted on a charge of stealing a handgun while making an eviction in January 1977. Ansell's chief assistant, Guy T. Williams, goes on trial next month on misappropriation and perjury charges in connection with the sheriff's department banquet.

Bobsib said the state intends to go ahead with the prosecution of both Barry and Williams.