He also defended Ishkanian's right to then take photos of the arrest.
"The fact she witnessed Ms. Locklear's erratic driving and reported it to the police did not mean she was disqualified from reporting the story, which she in fact did," Tepper wrote.
He said Ishkanian then sold the photos to celebrity gossip site TMZ for $27,000 - but did it through a third party, KM Press Group, because her standing in the industry has been damaged by a lawsuit against her former employer, US Weekly.
In its postings this week, TMZ questioned whether Ishkanian was "up to no good" and claimed she alerted fellow paparazzi to Locklear's impending arrest. TMZ head Harvey Levin said Wednesday that the owner of KM Press Group has repeatedly told him that one of the agency's photographers snapped the photos and that Ishkanian called to tip him off to Locklear's arrest.
Tepper said Ishkanian had been visiting family and friends in the Montecito area when she spotted Locklear's car driving erratically Saturday afternoon, called 911 and was advised by a CHP dispatcher to stop following the car.
But Levin said some of the pictures appear to be taken well before Locklear's arrest, and questioned Tepper's contention that Ishkanian just happened to run into her acting erratically at a market. At least one of the photos shows Locklear coming out of a shop.
Tepper initially said Ishkanian took all the photos after phoning authorities. But when pressed about the image of Locklear appearing to leave a store, he said he wasn't sure about the sequence that the photos were taken in, only that Ishkanian shot them all.
Levin said he did not consider the photos tainted. "Ultimately, these are photographs of an arrest."
The California Highway Patrol, which would not confirm the identity of the 911 caller, said she didn't identify that the driver was Locklear, but said the actress appeared "drunk" in a market. The CHP said in a news release that Locklear showed "obvious impairment," but alcohol has been ruled out.
Santa Barbara County prosecutors will have to decide whether to pursue charges after test results are returned that could show whether Locklear was under the influence of other substances.
CHP Lt. Dane Lobb said Wednesday that Ishkanian's involvement would not change what was going forward as a regular DUI investigation. "We determined (Locklear) was someone who shouldn't be operating a vehicle," he said.
Locklear's attorney, Blair Berk, did not return an e-mail message seeking comment Wednesday evening.
Tepper later said in an interview that Ishkanian also provided authorities with a statement and would testify against Locklear if necessary. He said Ishkanian sold the photos without disclosing that she was the shooter because of her $55 million lawsuit against US Weekly; that suit claims the magazine's employees damaged her career by accusing her of stealing information from company computers.
Federal agents later raided Ishkanian's home and business, but she has never been arrested or charged. Her lawsuit seeks damages for emotional distress, libel, slander, and conspiracy.
Tepper said Wednesday the US Weekly lawsuit has limited her business, claiming others in the industry refuse to use her material. The magazine is appealing a judge's ruling that refused to dismiss several of Ishkanian's claims.
US Weekly said through a spokesman Wednesday night that it had no comment.
After leaving the magazine, Ishkanian helped form Sunset Photo and News, a paparazzi and celebrity reporting agency.