can someones juvenile records that has not been sealed, be held against them for committing a petty theft as an adult
Admiralty / Maritime Attorney
You need to consult a criminal defense attorney. There are many variables involved and the answer can depend on things like the nature of the juvenile charge, the nature of the present charge, and what the prosecutor is trying to prove with those records. For example, if a crime was committed in a very specific way and a person's juvenile convictions wee all for doing exactly the same crime in exactly the same manner, it is very likely that the juvenile records would be ruled admissible. If the DA just wanted to admit them to prove the defendant was a bad person, then it is most likely that the records would not be admitted.
Consult with a good criminal defense attorney who can sit down and discuss with you the facts of your case, Your attorney will be able to answer you questions and advise you on how to proceed.
Criminal Defense Attorney
The answer is yes, but it rarely is.