In A Shock to the System, what is the significance of the lighter as murder evidence? Where did he lose it and why would it be evidence for the 2nd murder he committed?
He lost it in the rental car he used to frame George. He had swiped George's rental car card when he'd been out drinking at his retirement party so he could make a bogus rental car record. Lt. Laker heard about the lighter left in the rental car but he does not have it as evidence.
It was mailed back to the company for George, and Stella was going to forward it to him via the company mail carrier to the regular mail, but she starts thinking. Stella catches Graham in a lie about the lighter since he claims to have found it. Then she realizes something is fishy.
She plays a trick pretending to mail a pen so she can swap it out of the mail bin and replace it with the pen package. The reason the lighter is evidence for the 2nd murder, Benham, is that the car rental was a tool of misdirection so he could go rig the boat. He also used the barbiturates he got from the office clerk to knock Stella out so she didn't know he had gone down to the boat and back.
He intercepted the package with the pen in it and realized Stella had the lighter. I am not sure how the cops immediately tie George's rental car to the boat accident, (this was before GPS so why would the Lt. be aware of George Brewster's rental car?) and I am not sure how impersonating George to ask for a prescription refill of Senecal ends up killing him when he is in Grand Central Station.
One would have to assume I suppose that George is a lush and would take the pills and drink, which seems like a bit of a gamble.