Burger asks Stella Radom to testify to what Charlie Judd told her. Mason should have objected as that would be hearsay, especially since Judd was in court and ended up being Burger's next witness, where he denied saying what Stella had testified he said. Stella's words should never have even been heard.
Danny has resigned from the police force and then goes to visit Radom; yet he still has his police revolver, which is used in the murder.
Both Perry Mason and an impartial eyewitness see the future defendant in a murder case fleeing the murder scene. It is later established that the defendant was pursuing the actual murderer, but that person was not seen by Perry or the eyewitness.