Selena Gomez's alleged stalker just entered a not guilty plea in L.A. County Criminal Court -- and his bizarre conduct in court is further evidence ... he's unstable and dangerous.
Thomas Brodnicki -- who has a history of criminal stalking -- allegedly told his therapist he was going to kill Selena. Law enforcement believe he started stalking Selena back in July and poses a serious threat to Selena and her family.
Selena already has a civil temporary restraining order against Brodnicki. Today the judge issued a separate criminal restraining order prohibiting Brodnicki from going near Selena for the next 3 years.
Brodnicki is being held on $150,000 bail.