Excuse of documentary evidence!

Chairman of ACC Mr. Ghulam Rahman on October 7, 2012 in his remark before the TV camera brushed aside what the driver of the APS to the former Railway Minister Suranjit Sengupta said on the ground that his confessional statement can not be taken into cognizance to convict a person without any documentary evidence.
I cannot help wondering at what other documentary evidence does the chairman requires besides the found in the car that amounted to Tk. 74 Lac. Is he under the impression that it was a set-up and the driver is the major player in the incident? But the question is where the driver could manage such a large amount of money from, without the involvement of the high-ups?
If confessional statement is not good enough to accuse a person of a crime, according to the chairman of ACC, then how can the government convict the war criminals, who committed the crimes during the War of Independence, only on confessional statements without any documentary evidence?
I think, the bureaucrat turned chairman commented as such to please his mentors, which implies that the ACC, in essence, is not independent of government influence.