Everything can be convincing. IMHO, DNA part is the weakest one because it is a smudge of DNA found on one item that could be intentionally placed. I just read about Mo Wilson's case. Kaitlin Armstrong's DNA was found on the handlebars, the seat and the frame of Mo's bike. At the same time, there was neither Colin Strickland nor Cash left their DNAs there. So the question of transfer DNA is immediately closed. (Excellent job and presentation of TX LE, btw. They initially slightly dropped the ball, ending in the murderer's escape to CR, but towards the trial, were exceptionally professional).
If we ever heard, "BK's DNA was found on the shield, as well as in this, this, and this area of the house", it would be more convincing. The shield alone makes me wonder. As to the car and GPS, it is a strong point, if it is proven that BK had zero reason to be in Moscow. But here is the weakest point, the history of BK's addiction. He says, shopping is better in Moscow. And he is an addict who for the first time in his life is away from parental house. And there are places in Moscow where drugs are sold, and the King Road house was a party house. And the whole university area is rather small. If we imagine that BK's dealer lived next door to the victims or across the street, or even in the frat, his trips to Moscow can be easily explained. This is the weakness of the case. Some bridges between BK and the victims probably exist, but they are unseen to the public.