Clemenson was raised in Humbolt, IA by his father, Ernest, and his mother, Ruth, both of whom owed and operated a local drug store. A straight-A student in junior high, Clemenson had the grades to win a scholarship through his job as a paperboy for the Des Moines Register to the prestigious Phillips Academy in Andover, MA. Despite the distance from home, the experience afforded Clemenson both a world-class education and a love for the stage, which he would foster in hometown productions at Humbolt's Castle Theater during the summer. After graduating from Phillips, he attended Harvard, where he earned acclaim in the school's newspapers for his performances. In fact, future screenwriter Paul Attanasio singled him out for praise in an otherwise withering review of the Harvard Lampoon's sketch show.Clemenson followed Harvard with the Yale School of Drama before heading to Los Angeles to make his living as an actor. He began in television with supporting roles in "Fame" (Syndicated, 1982-87) and "The Paper Chase" (BBC/CBS/Showtime, 1979-1986) before segueing into features with roles in "Hannah and Her Sisters" (1986), "Legal Eagles, (1986) and "Black Widow" (1987). His precise delivery and knack for playing easily flustered characters made him a natural for professional types, often with a nebbishy or stuffed-shirt component to their nature. For much of the 1980s and 1990s, he was among the go-to character actors, playing Alex P. Keaton's English teacher on "Family Ties" (NBC, 1982-89), a reporter in "Broadcast News" (1987), a flight surgeon in "Apollo 13" (1995), as well as scores of lawyers, military men and other forthright types. One notable diversion was playing Socrates Poole, a mild-mannered Eastern lawyer who partners with a roguish bounty hunter (Bruce Campbell) on the cult Western comedy-drama, "The Adventures of Brisco County, Jr." (Fox, 1993-94). Clemenson also showed he could essay outlandish characters, such as the morbidly obese demon Balthazar in a 1999 episode of "Buffy the Vampire Slayer" (The WB/UPN, 1997-2003). Clemenson remained exceptionally busy on television throughout the new millennium, with appearances on countless top-rated shows, including "The West Wing" (NBC, 1999-2006) and "CSI: Crime Scene Investigation" (CBS, 2000-15). His television schedule kept him out of feature films for most of this period, with the notable exception of "United 93" (2006), which cast him as Thomas E. Burnett, Jr., one of the heroic passengers who stormed the flight cabin aboard the hijacked flight that crashed in a Pennsylvanian field during the terrorist attacks on September 11, 2001. Clemenson also won acclaim for his two-episode stint on "Veronica Mars" (UPN/CW, 2004-07) as a terminally ill man accused of murder.In 2005, Clemenson made his debut on "Boston Legal" as Jerry "Hands" Esperson, a brilliant but troubled lawyer with a laundry list of tics and quirks, most notably keeping his hands placed rigidly on his thighs - an odd habit that spawned his nickname. When first seen, he nearly killed Candice Bergen's Shirley Schmidt for passing him over as a partner in the firm; his defense case was taken up by Alan Shore (James Spader), who helps to bring to light the fact that Esperson suffers from Asperger's syndrome. By the third season, Clemenson had gone from recurring guest to series regular, and Esperson's struggles to contain his psychological quirks formed the backbone of his storylines. For his performance, Clemenson won an Emmy for Outstanding Guest Actor in 2006, and was twice nominated as Outstanding Supporting Actor in 2007 and 2009. He also shared Screen Actors Guild Award nominations with his "Legal" castmates in 2008 and 2009.