Born in West Hollywood, CA, Haas was raised by his father, Berthold, an artist who emigrated from Germany, and his mother, Emily, a screenwriter and former opera singer. From a young age, Haas wanted to be an actor. In fact, when he was in kindergarten, he came home from school and announced his intentions to pursue a career to his parents. Soon enough, he made his feature debut playing the youngest child of Jane Alexander in "Testament" (1983), a harrowingly realistic drama about the aftermath of nuclear war. The young Haas continued landing roles and made his first television appearance in the small screen movie, "Love Thy Neighbor" (ABC, 1984), before starring in "Ghost Train," the premiere episode of Steven Spielberg's anthology series, "Amazing Stories" (NBC, 1985-87). But his breakout role came with Peter Weir's excellent crime drama, "Witness" (1985), in which he played an eight-year-old Amish boy who witnesses a murder in the big city, leading a determined detective (Harrison Ford) to protect him and his mother (Kelly McGillis) from the corrupt cops out to silence him. Though his part was small compared to the film's two leads, Haas nonetheless made an impact on moviegoers, and for his impressive turn, received rave critical notices as well.Now viewed as the child actor du jour, Haas landed his first starring feature role with "Lady in White" (1988), a ghost thriller in which he was an imaginative boy confronted by both the supernatural and a serial child killer. He was equally impressive in "The Wizard of Loneliness" (1988), a World War II-era drama about a city boy sent to the country to live with his eccentric aunt (Lea Thompson) and uncle (Lance Guest), while his father (Don Johnson) goes off to war. Haas delivered one of his most emotionally compelling performances in "The Ryan White Story" (ABC, 1988), in which he played the titular 13-year-old hemophiliac who contracts the AIDS virus following a routine blood transfusion. Turning to the stage, he starred opposite Steve Martin and Robin Williams in Mike Nichols' revival of Samuel Beckett's "Waiting for Godot" (1988) at New York City's Lincoln Center. Meanwhile, Haas moved confidently into older teenage roles, particularly as an adolescent who receives an incidental introduction to the female anatomy from the title character (Laura Dern) in the coming-of-age dramedy "Rambling Rose" (1991). Also that year, he starred opposite Robert Duvall in "Convicts" (1991), a small period drama about an aging plantation boss (Duvall) at the turn of the century who keeps his farm afloat by using convicts as workers.The early 1990s proved to be a particularly awkward period for Haas, who had by this time moved with his family from Los Angeles to Austin, TX and spent most of his high school years out of the spotlight, save for a co-starring appearance in the Steve Martin comedy "Leap of Faith" (1992). He returned to the screen a few years later with roles in three new features, playing a prep school senior who becomes smitten by an older woman (Winona Ryder) in "Boys" (1996), while appearing in Woody Allen's musical comedy "Everyone Says I Love You" (1996) and Tim Burton's high profile 1950s sci-fi spoof "Mars Attacks!" (1996). After a small role in Terence Malick's lyrical war drama, "The Thin Red Line" (1998), Haas vacillated between film and television, appearing in "Breakfast of Champions" (1999), "Long Time Dead" (2002) and "Last Days" (2005) while logging episodes of "The Twilight Zone" (UPN, 2002-03), "24" (Fox, 2001-2010) and "Criminal Minds" (CBS, 2005-). When he was not appearing on screen, Haas became a noticeable constant as one of A-list star Leonardo DiCaprio's posse of close male friends, all of whom were photographed at one time or another courtside at Laker games or entering nightclubs. Meanwhile, Haas kept his focus on features for the most part, where he landed co-starring roles in a number of smaller thrillers and horror flicks like "Brick" (2005), "Alpha Dog" (2007) and "The Tripper" (2007). Haas next starred as a twenty-something slacker who becomes a vigilante after accidentally capturing a serial killer in the dark comedy "Gardener of Eden" (2007). Following a supporting turn in the horror thrillers "Death in Love" (2008), he was a murderous hooligan who terrorizes a suburban housewife (Kim Basinger) with three compatriots in the limited release, "While She Was Out" (2008). Due perhaps to his close friendship with the lead, Haas was next seen during the opening sequence of Christopher Nolan's mammoth hit, "Inception" (2010), in which he played a dream sequence architect employed by a corporate spy (Leonardo DiCaprio) who specializes in extracting valuable information by plunging into his victims' subconscious. Haas followed the Oscar-nominated "Inception" with a small part as Father August in the critically derided "Red Riding Hood" (2011), starring Amanda Seyfried in the titular role.