One who unexpectedly changes sides, e.g. a turncoat witness who is to testify as a friendly witness but suddenly, during trial, becomes a hostile witness.
TURNCOAT
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.
One who unexpectedly changes sides, e.g. a turncoat witness who is to testify as a friendly witness but suddenly, during trial, becomes a hostile witness.