7x20 - Alfred Hitchcock Presents

Vernon Wedge is an attorney who is approached by the father of Benjy Marino. Benjy is accused of stabbing another boy with a knife. Vernon decides to take the case, but his case for the defense seems hopeless until he discovers a special test that can determine if a knife blade ever had blood on it. He tries to conduct the test in court, but the prosecution resists. Even without the test, however, Vernon manages to get Benjy off. Later, Vernon decides to conduct the test in order to determine whether Benjy was really innocent. Before he can conduct the test Benjy's father arrives and cuts himself with the murder weapon. By doing so, he prevents Vernon from ever knowing the truth about the case.