While ‘the benefit of doubt’, ‘benefit of the doubt’ and other forms of this expression are popular, the correct form is ‘the benefit of the doubt’.
You give somebody ‘the benefit of the doubt’ because you cannot prove they are lying or you decide to trust them and believe the good thing(s) about them.
Examples:
- I will arrange another meeting because I’ve decided to give you the benefit of the doubt.
- Though the story is weird, we’ll give him the benefit of the doubt.