Word for someone who only tells the truth when it benefits them [closed]

What do you call people who speak the truth, but only for their own benefit?

Such a person might be described as "selective with the truth."

David Siegel on English Language Learners Stack Exchange describes it as meaning:

to tell some truths but not others about a topic. It at least implies that the result is to mislead, by omitting significant aspects of the whole truth.

Example usage:

And the bias here is that social network encourage people to be selective with the truth (at best) or to tell untruths. This can make it very difficult to gain real insight from social networks.