Two Big Plot Flaws
1. You do not send your most psychic law enforcement officer into the field. When doing so is very dangerous. When you can bring instead bring witnesses/suspects to her in order to extract information.
2. There is almost no way Dredd should be able to get the drop on the corrupt judges trying to kill him based on the information given in the film (i.e. no back story on corruption, or suspicion of Ma-Ma having judges on the payroll), and without the help of his psychic colleague. The corrupt judge makes a small slip of the tongue which is vastly more likely to be innocent than reveal anything significant and Dredd is immediately willing to kill him for it. He has nowhere near enough information to make that call. The corrupt judges do a terrible job of trying to kill Dredd given they know he doesn't know they are trying to do so.