Just as you wouldn't expect to go to a retail store and purchase a television that's been taken apart and replaced with bad parts, so you should get the same type of reliable product when you buy a used car. When your buying a new car, it should be all new.
Lemon laws vary from state to state, but most have the same guidelines and directives.
For instance, most cover incidences of the odometer being rolled back to hide the true mileage of the vehicle, if the auto was involved in a flood, had any kind of serious damage due to a severe accident, or any other reason, that was known to the dealer but not revealed to the consumer.
It's important to note that lemon laws don't apply to every defect in a car and to every car sold. If you purchase a car "as is" and sign an agreement to that effect, then the law does not apply to that sale.
Also, minor defects or problems with cars are not considered covered under lemon laws as they do not affect the car's overall performance or devalue the car to less than what you paid for it.
If you're concerned about whether or not lemon laws might apply to a vehicle purchase of your own, it's good to consult with a local lemon law attorney to get more specific information.
When your dealing with a car that might be a lemon the system can be complicated and confusing. It is always best to consult an attorney who has experience with the lemon laws of your state.