They said the holdouts changed their minds after the jury reenacted the scene ''as closely as possible'' in the jury room after Justice Kreindler denied the request to use the cars. He denied it after the chief defense lawyer, William M. Kunstler, declined to give his approval to the request.

An emotional scene accompanied the verdict. As Mr. De Sarno, a pale sharp-featured man in a black velvet jacket and matching vest, gazed intently at the jury, at least two jurors appeared to be crying. His mother, Marie, hurried from the crowded courtroom and fainted in the corridor outside. One of Officer Sledge's fellow policemen cried as another held him around the shoulders. Self-Defense Claimed

Mr. De Sarno faces a maximum term of 25 years to life when he is sentenced on April 6. In the two-week trial, he had admitted shooting Officer Sledge. But, contrary to the prosecution's charge that the defendant initiated the gunfire, Mr. De Sarno insisted that he acted justifiably in self-defense. He said he had fired only after he was first shot by the officer, who, Mr. De Sarno said, had been angered by an obscenity Mr. De Sarno had uttered at him.

Mr. De Sarno testified that, long before the night of the fatal encounter, Officer Sledge had harassed and threatened him to the point where the De Sarno family had complained to the police. Mr. De Sarno lived in Canarsie and Officer Sledge was with the area's 69th Precinct.

The defendant, who suffered two shoulder wounds, said he had inadvertently run over the fallen officer while trying to flee the scene and did not know he was dragging the officer's body. It had become caught in the car's undercarriage.