Any questioning in connection with a criminal case is frustrating. Not only do you need to ensure that you are being truthful, you also need to ensure that you are protecting yourself. Many people think that they can just say that they don't recall certain things and that will be the end of it. While you do have that right, you have think carefully about doing this.
There are only certain instances in which saying "I don't recall" is appropriate in a criminal case. The one point that is universal here is that you should only utter those three words if that is the truth. In other words, don't say that you don't recall something when you truly do.
That's one of the most important things about your defense -- everything must be based on facts. Lying when you are dealing with the criminal justice system can lead to trouble down the road.
On the other side of the issue is the fact that you shouldn't try to guess at the answers to questions. Everything that you say if you are on the witness stand or undergoing a deposition is that you need to only state facts. Trying to guess answers to questions can get you into a lot of trouble.
You might be able to invoke your Fifth Amendment right to avoid self-incrimination if your truthful answer to the question would incriminate you. This isn't something that you can use for one question and not another, so if you do invoke your Fifth Amendment rights, sometimes called pleading the Fifth, you should make sure that it is an appropriate time to do so and that you don't need to answer any other questions.
Source: FindLaw, "When Can I Say 'I Don't Recall' in Testimony?," George Khoury, Esq., accessed May 11, 2017