Mass Effect 2
Pressly's grandfather served in the First Contact War. He is not comfortable with non-humans (particularly the turians), but he is loyal to his commanding officer and will set aside those prejudices to serve the Alliance faithfully.
Pressly joined the Alliance shortly after he finished school, desiring to follow in his grandfather's footsteps. Before the Normandy, he was stationed on the SSV Agincourt, a frigate which was one of the first reinforcements to arrive at Elysium after the Skyllian Blitz (if Commander Shepard has the "War Hero" background, Pressly will reminisce about the Commander's involvement in the Blitz). After the crisis at Elysium, Pressly received his officer's commission and was selected by Captain David Anderson to serve on the Normandy as the Navigation Officer.
Mass Effect Edit
When Anderson gives Shepard command of the Normandy, Pressly becomes the Executive Officer (XO). He is in charge of the ship during the Commander's off-ship activities.
Though Pressly is loyal to the Alliance, he is more loyal to Shepard and finds the Commander's theft of the Normandy to be an adventure: "I can't believe we stole the Normandy! I know we'll all be court-martialed if this doesn't work out, but part of me loves this!"
At the start of the mission to Ilos, he detects Saren's position on the planet's surface, but argues against attempting landing efforts as there isn't sufficient open terrain to pull off a landing on the Mako.
Mass Effect 2 Edit
One month after Sovereign's attack on the Citadel, the Alliance sends Commander Shepard and the SSV Normandy to patrol distant systems for geth forces. Pressly believes that there are no geth and that the real threat is from slavers. While investigating a system where several ships have been reported missing, an unidentified ship attacks the Normandy. Navigator Pressly, on the bridge at the time, is knocked unconscious to the floor by an exploding console. After being revived two years later by Cerberus, Shepard is told that Pressly was among those who died in the attack.
Pressly's datapad can be found among the ruins of the Normandy crash site, at what used to be the command center. Some of the data is corrupted and unreadable, but the messages can still be understood. He states that he'd gladly die for any one of the non-humans on the ship and that his previous doubts — namely his uncertainty directed at Shepard for allowing aliens on board — were written out of ignorance.
According to Tali, Pressly acquired chicken pox at some point prior to his death.
Mass Effect 3 Edit
Pressly is listed on the Normandy SR-2's new memorial wall on the crew deck.