Continuity mistake: In one of the scenes after the grad students had poisoned their guest, Mark is squatting behind the table such that only his face is visible while he is talking to the others. Watch the wine glass beside him because the level of wine in it keeps changing between shots.
Continuity mistake: The group squabble at the table over how many they have killed, 9 or 10, with the latest victim still present with a knife in her back. Pete has the last word by taking off his jacket and shirt to reveal the upper part of his arm cast which has ten hash marks on it. He proclaims "It's ten." In that the woman just killed at the table made the tenth victim, how did he already have that tenth hash mark on his cast?