The 28-year-old Australian actor, who died after being found unconscious last January in his New York apartment, was posthumously honored for his toxic performance as the gleefully malicious Joker in the Batman saga "The Dark Knight."
"Menacing, mercurial, droll and diabolical," co-presenter Kevin Kline summarized as he listed Ledger, felled by an accidental overdose of prescription drugs, among the supporting actor nominees.
The actor's father, Kim Ledger; mother, Sally Bell; and sister Kate Ledger jointly accepted the award. "This award tonight would have humbly validated Heath's quiet determination to be truly accepted by you all here, his peers, within an industry he so loved," Kim Ledger said.
Kate Ledger said the family was accepting the award on behalf of "beautiful Matilda," her brother's 3-year-old daughter with actress Michelle Williams.
Even before "The Dark Knight" was released last summer, fellow actors, movie critics and others were predicting, and endorsing, an Oscar nomination for his chilling portrayal. While "The Dark Knight" received mainly positive reviews, many critics concurred that Ledger gave the movie a jolt of malevolent energy whenever he materialized on screen. Los Angeles Times film critic Kenneth Turan praised what he described as a "shocking, indelible performance."
Oscar history suggests that Ledger's award was not merely sentimentally motivated. Only one other actor ever has been posthumously honored with an Academy Award: Peter Finch for "Network" in 1977.
But it's likely that at least some academy voters were honoring not only Ledger's work as the Joker but also the breadth of his accomplished, if tragically brief, career. "With this premier performance as well as with a wide range of other roles to which he put his unique signature, Heath Ledger has left us an original and enduring legacy," Kline said.
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Over the last decade, Ledger demonstrated that he could handle comedy as well as serious dramatic roles in movies as varied as "10 Things I Hate About You" (1999), "The Patriot" (2000), "Monster's Ball" (2001) and "A Knight's Tale" (2001).
His career high point arguably was Ennis Del Mar, the emotionally terse ranch hand he played in Ang Lee's "Brokeback Mountain" (2005), for which he earned a lead actor Oscar nomination.
He had a tall assignment in interpreting the Joker, a character memorably incarnated by Jack Nicholson in Tim Burton's "Batman" in 1989. Nicholson's Joker is a witty, self-delighted clotheshorse, brimming with comic sang-froid.
Ledger's Joker is rawer and uglier, both physically and psychologically. Like Lon Chaney and other great monster men of the silver screen, Ledger conveyed a wrenching pathos lurking below the layers of makeup and venality.
In interviews, Ledger also acknowledged that filming "The Dark Knight" and another movie, "I'm Not There," had contributed to his ongoing bouts of insomnia.
Both in movie posters and in the minds of many viewers, the grotesquely smirking face of Ledger's Joker became the definitive image of the film. And, in one of those convergences of movies and real-world events, his nihilistic character spoke to the fears and uncertainties of a jittery time.
"See, I'm not a monster," Ledger's Joker tells Christian Bale's Batman during a brutal interrogation scene. "I'm just ahead of the curve."