In trial for firearm offenses, trial court improperly admitted evidence that defendant legally possessed firearms on other occasions. During a 2012 traffic stop, Jefferson (a passenger) was found with a firearm that was legally registered to him. Drugs and money were also found in the car. Based on this and other information, police obtained a search warrant for a Bentley that Jefferson had driven earlier. A loaded firearm that had been stolen and was not registered to Jefferson was discovered. He was charged with carrying a concealed firearm within a vehicle (Pen. Code, § 25400, subd. (a)(1)) and carrying a loaded firearm in public (Pen. Code, § 25850, subd. (a)). The charges included special allegations that he knew the firearm was stolen. (Pen. Code, §§ 25400, subd. (c)(2), 25850, subd. (c)(2).) At trial, the court permitted the prosecutor to present evidence of (1) Jefferson’s lawful firearm possession during the traffic stop and (2) a 2013 police contact where Jefferson was seen placing a bag with a firearm that he lawfully possessed in the trunk of the same Bentley. He was convicted. On appeal he argued that the trial court abused its discretion by admitting evidence that he lawfully possessed firearms. Held: Special allegations reversed. Although a defendant’s other acts are admissible in certain circumstances (see Evid. Code, § 1101), the other firearm evidence should not have been admitted in this case. Jefferson’s placement of his belongings in the Bentley’s trunk in 2013 did tend to prove that he was in control of the Bentley and its contents, but the nature of the item he put in the trunk was irrelevant. Additionally, the slight probative value of the firearm evidence to show that Jefferson knew the charged firearm had been stolen was substantially outweighed by the danger of undue prejudice. The error was prejudicial under the Watson standard with respect to the special allegations that Jefferson knew the firearm was stolen.