The Indiana court will use the rules of substantive law to determine if Sam is at fault in regards to Alex's injuries. Substantive law refers to the actual laws and legal principles that define people's rights and obligations.
In this particular case, the court will analyze the issue of fault in two different jurisdictions - Ohio and Indiana. When Alex had the flat tire in Ohio, Sam's Turnpike Service Station fixed it. Therefore, the court may examine whether Sam took reasonable measures to properly repair the tire, considering the applicable laws and regulations in Ohio. If Sam followed all the necessary standards and procedures required in Ohio, he may not be held at fault for the subsequent tire incident.
However, when the tire came off and Alex was injured in Indiana, the court will need to evaluate whether Sam's previous repair work was done negligently or if there were any other factors that contributed to the tire coming off. The court will consider the relevant laws and regulations in Indiana to determine if Sam's actions can be considered negligent or if he violated any legal duty owed to Alex as a service provider. This would involve examining whether Sam followed state regulations regarding maintenance and repair standards for motor vehicles in Indiana.
Ultimately, the Indiana court will apply the applicable laws and legal principles of negligence, duty of care, and breach of duty to determine if Sam can be held responsible for Alex's injuries. The court will assess the specific facts and circumstances of the case to arrive at a decision on fault and liability.