My opinion: a case like that should be fairly easy to argue. I suspect the turbo was installed on a car with significant mileage. Who's to say there wasn't a pre-existing mechanical issue? Secondly..unless the car came from the factory with either a turbo or supercharger, it likely does not have the pistons compatible (forged) with forced induction. A cast piston is not going to last long in a forced induction engine. Thirdly...when adding forced induction it becomes necessary to use higher (>87) octane gasoline or pre-detonation can occur. Pre-detonation all by itself can cause engine failure. If that's the case, then the turbo didn't cause the engine to fail...the owner's ignorance did. Anyway..I think you get the point. There are more than a handful of reasonable explanations that don't involve you being liable. That does not however mean you won't have to go through the expense of hiring a law professional.