Doc Strathmore is an agent with American Intelligence.
That's the best I can come up with. When we first meet him, he is being asked via a very covert way, to attend a highly secret meeting of some high-level government officials, invited by a Supreme Court Justice, which is rather unusual.
We learn later this:
"David Strathmore, code name DOC, was an elite covert agent tasked with finding traitors and often eliminating the problem. He was trained by the best spies in the world. Because some of the traitors were in the CIA, his training took place around the world. Charles De Gaul’s personal driver taught him defensive driving. Experts in the Mossad taught him weapons skills using anything from knives to exotic firearms. In Japan he learned hand-to-hand combat and how to make and use ordinary items as exotic weapons. A secure site in Silicon Valley taught him computer hacking techniques.
"Eventually, he retired from the active life of a spy, although the only way to retire was to die in that occupation. To live was to always be aware someone was going to try to kill you. Because of this possibility, Doc kept himself fit, trim and agile. He also kept up his skills with guns, blades and unarmed combat. His name was engraved on the Vietnam wall. A Supreme Court Judge and his secretary, Shelly Coyne, arranged all of the paperwork to enable him to live a normal life. There was a catch! If the sovereignty of the United States was endangered, the high court would convene. They would offer to reinstate his license to kill if he would take on the challenge. The United
States would pick up all expenses and offer any and all assistance. As he was officially dead, he did not have any pension or benefits. So Doc would be paid a fee of a considerable amount to compensate him."