I'm not looking for any particular crimes. Rather what kind of criminal behaviour particular person may be drawn towards.
Law enforcement agencies polygraph their potential members, and these agencies don't even have access to the vast classified info that DND personnel have access to.
As for the issue of "innocent until proven guilty" - if a person has got nothing to hide, then he/ she has got nothing to be afraid about. Secondly, being interviewed by a polygraphist can't be equated as being tried for a crime. It is simply part of the selection process and a condition of employment (in the agencies where it is used).
Coming back to the case of Sub-Lt Jeffrey Paul Delisle - this guy had been selling secrets since 2007. Now, I don't know if Intelligence personnel are polygraphed, and if they are then how often during their career. I can say, just purely based on statistics, that if the polygraphing was done routinely (assuming its done when an Intelligence Officer/ Member is first recruited), the chances of such a crime to be committed would have been minimized. Yes, as you've correctly pointed out - polygraphing is not a fool proof method.