Two Washington men who raped two women and abducted a third while posing as plainclothes police detectives were convicted yesterday in D.C. Superior Court of rape, kidnaping and sodomy. One of the men disappeared during the trial and is still at large.

In what Assistant U.S. Attorney William D. Nussbaum described as "the perfect scam," James R.C. Thompson, 26, and Stanley E. Humphries, 28, abducted three women at bus stops in three separate incidents, telling the women they were police detectives investigating a robbery case and that the women fit the description of the robbery suspects.

Thompson and Humphries were convicted yesterday of three counts of rape, three counts of kidnaping and two counts of sodomy. Thompson did not appear in court for the last two days of his trial and is still at large.

Both men face a maximum of six life sentences on the rape and kidnaping convictions and a maximum of 10 years each for sodomy.

Defense attorneys Henry Asbill and Ellen Kreitzberg maintained that in two cases Thompson and Humphries were mistakenly identified by the victims, and that in the third the victim consented to have sexual relations with the men.

Police Capt. Thomas Novak of the D.C. robbery division said yesterday that at all times when they are on duty, plainclothes police officers carry their badges and identification cards that show their photos, physical descriptions and fingerprints.

He said officers "are taught to properly identify themselves especially if they are in plainclothes" and citizens should ask to see this identification if they have any doubts.

Novak said police officers do not normally transport suspects in their private cars and usually use a marked police cruiser, patrol wagon, or unmarked car with a police radio in it.

He said police officers are not required to show an arrest warrant when they pick up a suspect but that one must be on file with the court.