In law, the Motive is the reason why an individual would commit a criminal act. In the AO universe, this translates to "The absolute undeniable proof why he or she did or did not do it". If the defendant has a weak motive, the prosecution has a near impossible case. If an attorney cannot establish a motive for an indicted witness, their accusation fails with a guilty verdict soon to follow. This completely disregards any decisive evidence that may be in the court record.