It's also what someone says to appease their friends and the friends and family of the convicted person. They regret having testified. They find that they are not popular after giving evidence, so they blame the police for what they did. What do you mean by 'put him up to it'. ? He must have some motive for getting somebody convicted by telling lies,. It's an odd thing to do without a motive. What was the benefit to him in it all ?.