Interesting article but...
...I question the validity of the approach.
1. If the person in question is incompetent to that extent then it's his management's fault for having left him in place to do the damage in the first place
2. If he's malicious then, again, I'd question what was going on in the workplace; there should always be checks and controls in place in any organisation (including monitoring motivation levels in your staff)
3. If it's a mistake then initiating a blame-game process won't help as the only winner will be he who covers his tracks best. Better to find out what happened, why and how it can be prevented in future.
If I did want to perform a forensic analysis to dig up some real malicious / incompetent behaviour then I am not sure that a HR consultant / recruitment agent (sorry, head-hunter) would be my first port of call regardless of their apparent self-believe / abilities. I'd probably start with an investigation's agency along with a forensic examination of any machines / logs. By the time Mr HR has had his chat there's time for all the evidence to have been removed.
Nice piece of self-promotion here though. Hope it works out well for you.
Just my two pence worth.