Philip Lem was sentenced to imprisonment in NCR Correctional Facility for a series of thefts at NCR camps. He was an integral part of the prison breakout, but believes the Powder Gangers should turn themselves back in since the gang won't be able to sustain themselves much longer.
Killing Philip Lem will cause all of Vault 19 to become hostile; even if you did so stealthily.
Philip seems to be the only source of tortiseshell glassesIn-game spelling, punctuation and/or grammar in the entire game. Though it appears that he does not always possess these glasses and may have ordinary sunglasses instead.
After you complete the quest Why Can't We Be Friends? (choosing Cooke's side and killing the fire Geckos), Lem will appear reduced to a pile of flesh. And some escaped convicts will say, "Too bad for Lem... Guts were flyin' everywhere..." It is possible to trigger a dialog with Cooke, after viewing the remains of Lem, in which Cooke admits to the killing.