Is there a word of phrase for someone who denies their own statement?
It’s like when somebody snitches and then denies having done so.
Recanter noun (formal) a person who makes a repudiation or withdrawal of a former belief or statement, esp formally in public (Collins English Dictionary)
from recant (v.) 1530s, from Latin recantare "recall, revoke," from re- "back" (see re-) + cantare "to chant" (see chant (v.)). A word from the Reformation. Loan-translation of Greek palinoidein "recant," from palin "back" + oeidein "to sing." (Online Etymology Dictionary)
In legal parlance, a witness can sometimes turn hostile or contradict himself.