outside man

plural outside men

1. An accomplice who locates a mark to be swindled by a confidence trickster.

   Wilson and Haines concerned in actually obtaining the money, Flynn outside man […]

   1901, Proceedings of the Parliament of South Australia

   2 more examples

   When he is shown that he can steal something from the outside man with whom he has already had contact he will say, "I don't feel that we should swindle him; he appears to be a nice chap."

   1956, Chic Conwell, Edwin Hardin Sutherland, The Professional Thief, page 71

   For example, one person may have a specialty in cooling off the mark, while another is able to lure in the mark with ease; these people may be referred to as the “roper” or the “outside man”.

   2012, Wilbur R. Miller, The Social History of Crime and Punishment in America

   Synonyms: roper