From The TimeSplitters Wiki

Male Trooper
Unlocked by	Beat Amateur League > It's a Blast > Demolition Derby with Silver or better
Species	Human
Size	Normal
Accuracy	7
Agility	6
Stamina	6
Fire Proof	N/A
Shock Proof	N/A
Default AI	4
Native TimeZone	2401
First Appearance	TS2 Arcade Mode
Relations	N/A
Games	TS2

TS1 Gesture	N/A	TSFP Gesture	N/A
TS2 Gallery	The Marine Troopers have borne the brunt of the TimeSplitters onslaught against humanity.	TSFP Gallery	N/A

Male Trooper appears to be an elite unit in the Human Forces. Though never featured in the Story Mode of TS2, their presence in the war is implied. It is also possible that Sergeant Cortez and Corporal Hart are members of the Space Troopers. In the Space Station story level in TimeSplitters 2 you have to pick up the suits in order to survive outside even though Sgt. Cortez and Corp. Hart's appearance do not change.