During an encounter with Benny Russell on the streets of Harlem in 1953, Mulkahey gave Russell a hard time about his nice suit and his drawing of Deep Space 9 before finally allowing him to go.
He was later encountered by Russell at a crime scene where Jimmy was found dead. When Russell attempted to push past the officers, Mulkahey and his partner Burt Ryan severely beat Russell. (DS9: "Far Beyond the Stars")
Mulkahey was played by actor Jeffrey Combs, who also portrayed Weyoun. Concerning the task of portraying Mulkahey, Combs stated, "At first, I wondered where I could find Weyoun in this guy, but then I realized that his status as a suppressing authority figure is the synthesis for Weyoun in Benny's mind. So I approached him as a completely different character." (Star Trek: Deep Space Nine Companion (p. 535))
Kevin's last name comes from the script.
The authors of the Star Trek Encyclopedia (4th ed., vol. 2, p. 58) thought Kevin Mulkahey "might have existed in an alternate reality, or perhaps only in certain reaches of Ben Sisko's mind."