What constitutes not cooperating? If graham just goes in answering "I don't know" to every question who are we to say he is lying?
I'd say making yourself available when they ask and giving an answer to every question asked of you (baring in mind "I don't know" is a valid response) is about as much cooperation as anyone should be expected to give in these situations.
I'm not talking about any individual or any particular situation in the following.
If investigators (of any kind) put evidence on the table that it is clearly obvious a person should have some knowledge about, and they give it the "I don't recall" defence, then they are not being co-operative.
There are circumstances when a person should reasonably be expected to recall their actions to an extent IE if there is footage of them on camera, signed statements, credit card/bank receipts, phone/internet records, medical records, etc.
Investigators will often ask Q's, get the stone wall, then present evidence, then ask the Q's again.