He urged the judges to send Mr Kenyatta's case back to the pre-trial chamber for judges to assess what remains of the evidence - and decide whether it is substantial enough to justify a trial.
"To a certain extent we have lost faith in the decision-making as we warned the pre-trial chamber of the quality of the evidence and we were ignored, " Mr Kay told the court, reports the AFP news agency.
You enter it by a stairway reminiscent of pre-Roman burial sites, pass through a narrow corridor and enter an imposing square burial chamber with a pink marble granite sarcophagus in the centre.