must, can't and might have

1 . The students might ____________________ ____________________ to the classes .
2 . We ____________________ have ____________________ that before .
3 . The police detained her , but I knew it ____________________ have ____________________ a mistake .
4 . The reporter presented the story , he ____________________ have ____________________ evidences .
5 . He ____________________ have ____________________ messages , he doesnt have cellphone .