Here is a simple tip for framing questions.
Once a lawyer has established that a witness was present at an event, he or she might ask a poor follow-up question along these lines: "Do you remember what happened?"
Other versions of the wrong way to follow-up--
"Do you recall ... "
"Are you able to remember ..."
"Can you recall ..."
Questions like these too easily give the witness an opportunity to evade by answering, "No, I don't remember."
There's no need to give the witness a choice not to remember. Instead, get to the point: "Tell us what happened at the meeting on May 6" or, simpler yet, "What happened at the meeting on May 6?"
Some witnesses may not remember what happened. If not, they'll let you know. In the meantime, there's no reason to invite the witness to "dis-remember" in the way you ask the question.
Source: Ashley Lipson, Guerrilla Discovery §10.52 (James Publishing)