Elmer was an engineer who worked for the DHARMA Initiative in 1977, and he was eventually killed during the purge. The character was an uncredited background cast (extra) role, and the name is known only from the wardrobe label. The role was played by actor Niv Rabino in season 5, and an unidentified actor in season 3.
Elmer was first seen writing on a clipboard while welcoming new DHARMA recruits outside the processing center. ("Namaste")
He was present at the meeting where the execution of Sayid was put to a vote. Elmer, along with everyone else in the room, voted for Sayid's execution. ("He's Our You")
Elmer was moving equipment and being debriefed by Horace in the aftermath of Sayid's escape during the flaming DHARMA van attack. ("Whatever Happened, Happened")
He was seen in the background during Roger and Kate's conversation regarding Ben's disappearance. ("Some Like It Hoth")