From the law firm of Quinn Emanuel: "Hitting the Target--Maximizing the Effect of Impeachment"--
The question "How do I maximize my impeachment" arises in a variety of circumstances—but always, and most critically—when it comes time to impeach a witness’ trial testimony with a prior inconsistent statement, such as a deposition or a writing authored by him. The standard trial advocacy books almost uniformly suggest a single formula for such impeachment. It is a formula which usually works, but to which QEUO&H recommends adding one element, and amplifying another.
The article goes on to discuss the problem of establishing that the prior inconsistent statement is more reliable than the trial testimony.