Some decisions in the criminal justice system are more difficult to make than others. One of the more difficult ones in many cases is whether the defendant should take the stand to testify. There are many reasons why this might come up, but one of the most common is so that the jurors can hear the defendant's side of what happened at the time of the incident that is central to the case.
One school of thought is that if the defendant takes the stand to give his or her side of the story, he or she might seem more like a person to the jury instead of seeming like the case is just a culmination of facts. This is important in some cases because the jury might act in a more favorable manner when they have a "personal" take on the defendant. Of course, there are some instances in which this might work against the defendant so the defense attorney needs to look at this from every angle possible.
A primary reason to keep a defendant off the stand is when there is some belief that the prosecution will ask a question that might be impossible to answer. This might be one that makes the defendant choose between lying on the stand, which is perjury, or telling a truth that could damage the defense.
Many people think that the defendant can just plead the Fifth Amendment when he or she doesn't want to answer a question. This is a misconception. If a defendant is going to plead the Fifth, he or she can't answer questions at all. The only answer is that they are pleading the Fifth Amendment. While this shouldn't impact the defense's case in theory, there is a chance that it will in practice.
Since there isn't a checklist that defense attorneys can use to determine when a defendant should take the stand, they must consider each factor in the case to come up with a plan. If there is a chance that the defendant will take the stand, the defense attorney should prepare accordingly.
Source: The New York Times, "When to Put the Defendant on the Witness Stand," Peter J. Henning, accessed Jan. 03, 2018