Maybe the increased reward, if highly publicized and clearly communicated, will at least get the case back in the media and perhaps motivate someone to check their own security cameras or revisit that week-end mentally. Maybe someone who assumed this has nothing to do with them, so why bother, will give it more thought. Or, maybe this potential "hoodlum" does know something and will be willing to contact LE. You know, turn over a new leaf in life, get a fresh start. Maybe a wife or girlfriend of the perp. has suspicions but couldn't get involved due to her financial dependency on the perp. I would guess that the perp., if he has a romantic partner or spouse, is highly controlling and perhaps abusive towards his partner. The reward could motivate such a partner to contact LE.
Maybe if there are two perps. one is the weaker partner in the crime and news of an increased reward may get him or HER to entertain thoughts of contacting LE. Maybe the weaker partner didn't kill but was involved some other way and thinks they would not be charged with murder. Could interpret news of the increased reward as an indication that LE would have resources available to help him or her out of a mess that they didn't intend to find themselves in.
Maybe. Maybe. Maybe.
Maybe, if nothing else, it sends a message to the perp. that they are still working the case. He must be feeling smug, perhaps even amused by the apparent failure of LE to figure this all out. This could be a smoke screen to let the perp. THINK they have nothing.
