Tamper

The definition of "Tamper" is to interfere improperly. (Tampering with a document.)

Additional Sources

Answers.com

To meddle, alter, or improperly interfere with something; to make changes or corrupt, as in tampering with the evidence.

Duhaime Legal Dictionary

The term "jury tampering" means to illegally disrupt the independence of a jury member with a view to influencing that juror otherwise than by the production of evidence in open court.

FindLaw

1: to bring improper influence to bear (as by bribery or intimidation) (used with with) Example: tampered with the jurors

2: to alter or interfere in an unauthorized or improper manner (used with with) Example: tampered with evidence