The trial of former Liberal Party leader Jeremy Thorpe, suddenly shortened by his refusal Thursday to take the witness stand or offer any evidence in his own defense, could end as soon as next week.

Beginning on Monday, closing arguments will be made by prosecutors and defense lawyers for Thorpe and the three businessmen on trial with him on charges of conspiring unsuccessfully to murder former male model Norman Scott.

After hearing the judge's instructions on the complicated law of criminal conspiracy, the jury will decide whether the four conspired, at Thorpe's urging, to have Scott killed because he threatened to make public a homosexual affair he claims to have had with Thorpe.

Scott and other witnesses at the trial testified that Thorpe had an affair with Scott, that he became upset when Scott repeatedly asked him and relatives and friends for money and that he plotted to kill Scott when payments apparently failed to satisfy Scott.

When it came the turn of the defense Thursday to present its case after nearly three weeks of prosecution testimony, only one defendant, Welsh slot machine distributor and nightclub owner George Deakin, took the witness stand. He testified that he never had known of any plot to kill anyone and had been asked to find a person only to "frighten the hell" out of someone who was never named.

But lawyers for former Liberal Party treasurer David Holmes and the fourth defendant, Welsh carpet store owner John Le Mesurier, said they would present no testimony on behalf of their clients. Then, just before court was to adjourn for the day, George Carman, Thorpe's attorney, announced that "On behalf of Jeremy Thorpe, I call no evidence."

Thus, the Thorpe trial was deprived of Thorpe's testimony, the only drama that had not already been thoroughly previewed in an unusually public and detailed preliminary hearing of the case in a provincial magistrate's court late last year. CAPTION: Picture, Jeremy Thorpe enters London's Old Bailey court.UPI