The icon.
"Erm John, you didnt have a moustache this morning..."
Suspicious is an unlockable passive ability. Once acquired it negates any chances of 
sabotage or friendly fire, additionally granting +200 
Initiative per enemy 
Spy deployed. A very handy pick, considering that it counters 2 (think about it) of 8 available classes, and not just any replaceables, but 2 quite popular ones. If that's not good enough, he can't be shot in the back by his fellow dummies during close quarters such as Extermination missions usually are.