In the case of Cobert v. New York, 1966, the U.S Supreme Court examined whether a defendant's constitutional rights were violated when they were not allowed to cross-examine their own witness. The defendant was charged with burglary and attempted grand larceny after being found in possession of stolen goods from a warehouse. During his trial, he called an accomplice as a witness who testified that he had acted alone in committing the crimes and that the defendant was unaware of them. However, when inconsistencies arose during this testimony, the judge refused to allow defense counsel to cross-examine him on these points due to state law prohibiting defendants from impeaching their own witnesses' credibility. The Supreme Court ruled against Cobert by upholding his conviction on appeal. They concluded that while it is generally true under federal law and many states’ laws that parties may not impeach their own witnesses without showing surprise at damaging testimony given by those witnesses; there are exceptions which permit impeachment if certain conditions exist such as where statements made by a party’s witness affirmatively damage its case or where contradictions arise within direct examination itself.

In the dissenting opinion for Cobert v. New York, Justice Harlan argued that the majority's decision was a departure from established legal principles and precedent. He contended that it was not unconstitutional to try an individual twice for different offenses arising out of the same act or transaction, as long as each offense required proof of a fact which the other did not. In this case, he believed that assault and attempted robbery were distinct crimes with separate elements needing independent proof; thus double jeopardy should not apply in this instance. Furthermore, he expressed concern about potential negative implications on law enforcement if prosecutors had to consolidate all charges into one trial whenever multiple offenses arose from a single event or transaction.