O.J. Simpson's friend Brian "Kato" Kaelin testified today that he heardthree mysterious "thumps"outside his guest house residence in the Simpson compound at about 10:40 p.m. on the night Nicole Brown Simpson and her friend Ronald Goldman were killed. Describing the sounds,Kaelinsaid he was frightened at first, but felt better when he went to investigate the noise and saw a limousine driver waiting for Simpson. Prosecutors contend the noise, in an area where police said they later found a bloody glove, was O.J. Simpson returning from committing the murders.