What is the motive?

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Across
  1. 3. Something that proves you did not comit
  2. 8. Something you don't know or understand
  3. 9. A type of weapon
  4. 10. Tool used to hurt someone
  5. 11. The pattern on your finger
  6. 12. Why someone did something
Down
  1. 1. A bad thing that is against the law
  2. 2. A person who was hurt during a crime
  3. 4. A liquid that can kill you
  4. 5. Someone who kills another person
  5. 6. A person who investigates crime
  6. 7. A person who might have committed a crime
  7. 12. To kill someone