A convicted Washington heroin dealer was found guilty of second degree murder in Prince George's County yesterday in the fatal shooting of a man allegedly suspected of stealing heroin from another D.C. drug underworld figure.

A Circuit Court jury deliberated four hours before convicting Charles Watkins, 22, of Southeast Washington in what a prosecutor described as the "execution style" slaying in June 1981 of Eddie Harris, 24, of Northeast Washington in a park near Capitol Heights.

Sheriff's deputies maintained a close guard over the courtroom during the three-day trial after a threat was made against the life of a key prosecution witness. The witness, Ronnie Wilder, who is serving a 21-year bank robbery sentence in Alabama, testified that he saw Watkins fire five shots at Harris.

Prosecutor David Simpson said in court that Watkins shot Harris because Harris was suspected of stealing from another drug dealer.

Watkins' attorney, William J. Parker Jr., said his client was innocent and characterized Wilder's testimony as retaliation because Watkins had stolen Wilder's girlfriend.

After his conviction Watkins, who had been charged with first degree murder, told a reporter that he was innocent. Watkins also was convicted of false imprisonment and illegal use of a handgun.