Rosa Lopez, the witness who may provide O.J. Simpson with an alibi, began her testimony this afternoon. Defense attorneys say the former housekeeper for a Simpson neighbor will state that she saw Simpson's Bronco parked outside his home at the time when the murders allegedly took place. Judge Lance Ito allowed her testimony to be videotaped for later viewing by the jury, which was not present in the courtroom as she answered questions today. Ito permitted this unusual arrangement so that the Lopez testimony for the defense would not interrupt the presentation of the prosecution's case.