when does a process enters a blocked state
Process state A process transitions to a blocked state when it cannot carry on without an external change in state or event occurring. For example, a process may block on a call to an I/O device such as a printer, if the printer is not available. Processes also commonly block when they require user input, or require access to a critical section which must be executed atomically. Such critical sections are protected using a synchronization object such as a semaphore or mutex.
Exclusionary rule It was not until Mapp v. Ohio[18] in 1961 that the exclusionary rule was also held to be binding on the states through the Fourteenth Amendment, which guarantees due process. Up until Mapp, the exclusionary rule had been rejected by most states.[19]