If the defendant impedes the probation officer's investigation, e.g. by failing to disclose all prior convictions and arrests, his sentence may be increased for obstruction of justice and failure to accept responsibility, even if the undisclosed information has no effect on his criminal history score. Since some defendants may not remember all such prior history, some defense attorneys conduct their own investigations. Some courts have ruled that a defendant waives his Fifth Amendment right against self-incrimination when he pleads guilty. It remains to be seen exactly how this applies to presentence investigation interviews, but it appears likely that a defendant who refuses to talk about his criminal history will jeopardize his sentence reduction for acceptance of responsibility.