Moreton was spotted putting the drone into the boot of his Audi but he drove up a dead end and the officers blocked his escape.
He clambered over a six-foot fence to try to escape and used his remote locking key to deadlock the car with the active drone in the boot.
Moreton claimed he was near the prison in the dead of night because he believed Romanian circus performers had stolen one of his pet chihuahuas.
He said: "We were told the circus left the dogs outside at night. As daft as it might sound, I brought the dog's father, Archie, to see if he could find it."
Moreton then claimed he was found in the bushes because he had downed a litre of vodka and had collapsed in the middle of the dog-hunt.
He said he had been using the drone to search the riverbank for the dog.
The 33-year-old was heard rustling in the undergrowth after prison officers chased the 70mph drone away from the outer wall of Perth Prison.