An Alexandria man whose 1976 drug conviction was overturned because his wife engaged in a sex act with a former prosecutor in the hopes of getting her husband a light sentence was sentenced yesterday to a 90-day work release program.

The plea of Daniel Chenault to the original drug charge he had faced apparently brings to an end a series of events that surfaced shortly before former Alexandria prosecutor William L. Cowhig abruptly resigned from office in February, Sherry Freedman Chenault told authorities at that time that she had accepted Cowhig's sexual advances in the hope of getting a light sentence for her husband, who was facing a charge of distributing the drug PCP.

When Chenault originally pleaded guilty to the charge in 1977, he was given a five-year prison sentence. Yesterday Alexandria Circuit Court Judge Donald H. Kent technically gave him a 10-year sentence, but credited him with nearly four years he had spent in prison, suspending the rest of the sentence, and then placed him in the work-release program.

Cowhig resigned shortly after allegations about the sex incident were revealed. A special prosecutor, appointed to investigate the incident, found no cause for criminal prosecution, but referred the case to the Virginia State Bar, whose report has not been released.

Cowhig has consistently denied the allegation.