One of the prime reasons to spend the time and money to depose an adverse witness should be to gather impeachment material. Other than hiring a private investigator to delve into the witness's past, the deposition is the most effective tool in the lawyer's arsenal for uncovering dirt and chipping away at credibility. that includes attacking an eyewitness account, challenging an unfavorable opinion, exposing bias, and undermining believability. Yet most lawyers don't ask all of the basic, open-ended questions tha tcould help achieve their impeachment goals. These "killer" deposition questions should be asked of adverse witnesses in every type of case.