Do police have to knock before entering?

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Tags

1. #announced
2. #answer
3. #without
4. #waited
5. #required
6. #seconds
7. #knock
8. #first
9. #someone
10. #police
11. #announce
12. #reasonable
13. #person
14. #entering
15. #hudson
16. #knocking
17. #before
18. #enough
19. #themselves