Might have vs Must have
Express varying degrees of certainty about past events What Happened? MIGHT HAVE Might expresses an opinion: an uncertain guess, a speculation, based on very little information. Might have expresses an opinion about an earlier (past) situation. A GUESS The car driver might have tried to pass between two buses. One of the bus drivers might have changed lanes without looking first. The bus drivers might not have been able to see the smaller, lower car. The road might have narrowed and so they all tried to move into the same lane. MUST HAVE Must expresses an opinion: an inference, a conclusion, based on known details. Must have expresses an opinion about an earlier (past) situation. A CONCLUSION The car driver must have panicked when he saw the buses moving in on both sides. The bus passengers must have heard a crunch. (sound) ...