Idiom that describes a person who doesn't have an acceptable witness

We Persians have a proverb that says:

They asked the fox, "Who's your witness?" The fox said, "My tail!"

What do Americans say when a person only has their ally as a witness? Is there any idiom for this?

Solution 1:

I don't know any relevant idioms, but unvouched-for would be understood by all native speakers. Depending on the exact context, maybe uncorroborated, or unsubstantiated might fit better.

Solution 2:

Referring to someone as having "no alibi" is said so much that it is almost an expression, I should think.

Solution 3:

An idiomatic phrase, albeit one with multiple meanings, is in his back pocket. This is the sense used in headlines like Romney Has Drudge Report In “Back Pocket”, Says Thompson and Top Senate Democrat Tacitly Acknowledges He Has Angus King’s Vote In His Back Pocket. Note: As suggested in a comment about in one's pocket referring to in one's control or possession, it appears that pocket alone (without back) is also suitable. For example, "Witness X is in Y's pocket" (or back pocket) means X may be a suborned witness. Note 2: American Expressions by Billy R. Lawson lists "I have him in my hip pocket" as meaning "He owes me some favors".

Besides some terms previously mentioned, also consider perjurer, cover story (in sense "A fictitious account that is intended to hide one's real motive"), and paid witness.

Note: Regarding already-suggested no alibi, from time to time one hears phrases like Alibi Al applied to alibied persons, and Alibi Guy applied to people supplying alibis (alibiers?).

Solution 4:

In such a case it could be said that the witness was 'in his ally's corner' or that the witness 'had his friend's back'. In the first case the implication is that the witness would tailor his evidence to support his ally; in the second that while the witness would support his friend through thick and thin he may not be prepared to bend the truth in so doing.

Solution 5:

The direct answer to your question is that the English language has no idiom I have ever encountered that describes the person who does not have an independent witness for him.

As others have offered, we do have plenty of idioms to describe the person who is the tail. Just not the fox.