I saved the game just before going into the interrogation room where Lambert was being held.
I then tried both scenarios (Kill Lambert, Kill Jamie)
Why couldn’t I shoot the light or the camera? Then I could have disabled Jamie and got a retina-scan of his eye right there! (But no… For some reason this dilema suddenly makes Sam go nearly blind and renders him unable to lift his shooting arm higher than the vertical or to the left)
Killing Jamie gets you instant blown cover. Everyone in the compound is after you.
Shooting Lambert retains your cover and doesn’t lose you any trust with the NSA.
Having spent the entire game carefully keeping my trust with both organisations fully intact I decided to shoot Lambert… Thinking that he might be wearing some kind of Bullet Proof vest (though in hindsight the JBA would have found it and removed it) and that I would have chosen (being hyper-skilled) to shoot him in a non-lethal area of his chest and he would survive.
The last level was fun as I was able to just rush up to people (as they assumed me friendly) and knock them out with a Sam-Punch. The last bit was irritating… two guards guarding the bomb… Another break from habit was required here… Habitually I use stealth and disable any guards. Not once shooting my gun at anyone. But here I just head-tapped both of them… then sprayed bullets at Dufrain.
But I wonder - Why didn’t Lambert have me just do all this in the beginning? Why did I have to do all that stuff to help the JBA?