You know something about a crime — and the prosecutor wants you to testify in court. Your concern, however, is that you may not exactly have “clean hands.” You’re worried that what you say could eventually come back to haunt you.

In situations like these, the word “immunity” may get tossed around, but you need to make sure you understand exactly what type of immunity is being offered.

What is use immunity?

This is a narrow form of immunity that prohibits prosecutors from using any of your testimony in court — or any evidence that may have been derived from that testimony — against you.

In theory, it’s designed to protect you just as much as not testifying at all. However, there’s a catch: You can still be prosecuted for any crimes you mention as long as the prosecutor comes by their evidence another way.

For example, maybe you got mixed up in a robbery that turned into a homicide. You testify against the ringleader of the gang involved. Your testimony can’t be used  — but if video evidence turns up that shows you on the scene during the incident, that evidence can be part of the prosecution’s case against you.

What is transactional immunity?

This is the kind of immunity that most people think of when they hear that the prosecutor is offering immunity in exchange for their testimony.

With transactional immunity, you’re protected from charges related to your immunized testimony. For example, maybe you played a role in luring the robbery victim mentioned above to the spot where they were ultimately killed. You could fully testify to your part in the scheme and remain immune from prosecution — even if the prosecutor later finds independent evidence of your involvement.

Don’t ever let yourself get talked into a bad deal by a prosecutor. Having a defense attorney by your side when you’re facing serious charges is the smartest thing you can do.