protesting too much

Sometimes when a defence lawyer makes an argument that is too strident, it undermines their case. They thoroughly expound every possible exculpatory factor, they forcefully refute every single possible inculpatory factor. They pounce on every opportunity to make their case and raise every possible objection, and it gives you the impression that their client is not innocent, because they have to work so hard and grasp at every straw to prove their innocence.