I wouldnt put it past them, but on the other hand writing while under pain killers will not appear the same as a sober one.
Occams Razor seems to apply here.
Cummings would probably make more sense while under morphine than he would normally.
Think it would be a good argument that he was not of clear mind to sign anything, especially something that serious, while under the influence of any narcotic. Should be void if that is ever said.
Uh, he used that to snort coke...