TAMPERING

To make unauthorized or improper alterations, sometimes causing deliberate damage; to meddle (with something).

"The alarm had been tampered with and didn’t go off when it should have."

To try to influence someone, usually in an illegal or devious way; to try to deal (with someone).

"Prosecutors argued that he would tamper with witnesses if bail was granted."

To meddle (with something) in order to corrupt or pervert it.

The act of one who tampers.