take for dead

take someone for dead

to assume that someone who is still alive is dead. When we found her, we took her for dead, but the paramedics were able to revive her. He was taken for dead and abandoned. take someone for someone or something to perceive someone as someone or something. I took you for a fairly even-tempered person. You aren't. Alice took Jim for a gentlemanwhich he was.
See also: dead, take