Has it ever been speculated by LE that GGK filmed or photographed his assaults?
Also wondering if he might have had a tape recorder in order to play the sound of voices so that the victim would think he was not alone?
speculation, imo.
Yes, and the EAR definitely stole some expensive camera equipment, at least once from a victim's house.
Prior to his arrest LE / the FBI have always said there were two elements of his MO which they were keeping secret, to weed out false confessions, help distinguish his actual crimes from copycats etc...
I have seen numerous people over the years speculate that one of the 'undisclosed' features of his MO was that he took photos of the victims. But it is still only speculation at this point.
ps In the past couple of days lots of people have bee saying that they believe the two secret MO's were turning on the kitchen faucet and running a fan to disguise the sound of his departure from the house. While he definitely DID do these two things (as described by victim Margaret Wardlow) I don't believe they would be unique enough to chose as his 'undisclosed' features of his MO.
My own opinion, as always.