It has long been the law in Missouri that witnesses cannot be impeached on collateral matters except certain criminal convictions. What does this mean in non-legal terms? Basically, during cross examination a lawyer cannot try to make you look dishonest by referring to a dishonest statement or act that has nothing to do with the case or facts at hand, unless it is a criminal conviction. Meaning, you cannot be impeached for an alleged lie or dishonest statement that would not otherwise be admissible, so of the impeachment evidence would not be admissible for any other reason, then it is not admissible for impeachment.
This changed in 2010 with a new Missouri Supreme Court ruling in the case of Mitchell v. Kardesch, 313 SW 3d 667 (MO 2010). This was a St Louis medical negligence case wherein the defendant doctor inaccurately stated (i.e. lied) in written discovery about his medical license being suspended. Typically, suspension of a medical license may not be admissible at a medical malpractice trial, however, the Plaintiff's lawyer attempted to impeached the defendant doctor during cross examination on the basis that he answered in written discovery that his license had not been suspended when it actually was. As expected, the trial court judge ruled that the Plaintiff's attorney would not bring this up in front of a jury as it was impeachment on a collateral matter.
It has long been the rule in Missouri that on cross-examination a witness may be asked any questions which tend to test his accuracy, veracity or credibility or to shake his credit by injuring his character. He may be compelled to answer any such question, however irrelevant it may be to the facts in issue, and however disgraceful the answer may be to himself, except where the answer might expose him to a criminal charge.
Common forms of Impeachment:
Evidence showing witnesses inability to perceive or memory. Think My Cousin Vinny scene where he impeached the witness with the thick glasses and challenges her ability to see clearly. Another Cousin Vinny example, the impeachment of the male witnesses based on his inability to perceive time, this was shown through his inconsistency with the time he testified to the events occuring and the time it took to cook his grits on the stove at the same time. Also, drug or alcohol use falls under this category as well.
Admission of Evidence of Prior Convictions. This is a common form of impeachment, in Missouri convictions are admissible to impeach the witnesses. As a practice tip, I typically reserve the prior convictions to crimes that go to honesty, such as theft or stealing; attacking a witness on any crime may garner sympathy from the jury as it may appear you are unfairly beating up on them.
Admission of evidence of the witness's bias, interest or prejudice. This is the situation of personal relationship with a party, financial interest, or evidence of acts or statements that tend to show bias toward one party or another.
Admission of Prior Inconsistent Statements. Pretty easy concept, witness previously testifies inconsistent with present testimony.
Admission of Evidence of Witnesses' Character for Truthfulness or Veracity. This is the more broad and vague basis that was expanded by the recent ruling on the Mitchell v. Kardesch case. This does not include general moral character, but evidence of the witnesses ability to tell the truth. The scope of the issues able to be brought up has been limited int he past by several cases including State v. Wolfe, 13 S.W.3d 248, 258 (Mo. banc 2000), stating:
"The impeaching testimony should be confined to the real and ultimate object of the inquiry, which is the reputation of the witness for truth and veracity. In other words, specific acts of misconduct, without proof of bias or relevance, are collateral, with no probative value."
Over the next several years we will see how this new case opens up the ability of lawyers to get into collateral issues on cross examination in the name of impeachment.