In some circumstances, prior criminal records can be brought up. They can't be used to prove you did the new crime--e.g. the fact that you committed past crimes does not mean you committed a new one--but they can be used:1) To impeach you, or prove your lying, if relevant; for example, say you claim you are not violent and have never committed a crime of violence--the fact that you carjacked previously can be brought up to show that claim was a lie.2) If the prior crime shows some sort of pattern of behavior--suppose in the carjacking and other crimes, you used a lead pipe; if in the current case, the person was injured by a lead pipe, it may be that the prior crimes can be brought up to show that you tend to use a lead pipe as a weapon.3) To show physical ability--say you claim you are not strong enough to have injured the person in the current case, but you beat someone badly in a prior case; it may be that the prior case could be brough up to show that you are physically capable of this.