The argument might hold up in court if the yahoo had a good lawyer. All that's known at the moment is he was followed by a suspicious stranger who bought him lunch. Nobody can positively identify the stranger. Restaurant employees either didn't get a good look at him or said he could have been anybody. Robbery doesn't appear to be a motive.
Nothing appears to be a motive.
This may turn out to be an impossible crime to solve. The perfect murder, so to speak. Even Leopold and Loeb weren't so diabolically cunning in their ideal execution. While moving I was beeped at by a driver in a late-model luxury Toyota, at my side. I wondered why.