Opinion of the Court
a series of state and federal cases, the Restatement (Second) of Torts, and prominent treatises that discussed secondary liability in tort. Id., at 476–478, 481–486. With respect to aiding and abetting, the court synthesized the cases as resting on three main elements: First, “the party whom the defendant aids must perform a wrongful act that causes an injury.” Id., at 477. Second, “the defendant must be generally aware of his role as part of an overall illegal or tortious activity at the time that he provides the assistance.” Ibid. And, third, “the defendant must knowingly and substantially assist the principal violation.” Ibid. (citing, e.g., Landy v. Federal Deposit Ins. Corp., 486 F. 2d 139, 162–163 (CA3 1973); Woodward v. Metro Bank of Dallas, 522 F. 2d 84, 94–95 (CA5 1975)). Halberstam then articulated six factors to help determine whether a defendant’s assistance was “substantial.” 705 F. 2d, at 486–488. Those factors are (1) “the nature of the act assisted,” (2) the “amount of assistance” provided, (3) whether the defendant was “present at the time” of the principal tort, (4) the defendant’s “relation to the tortious actor,” (5) the “defendant’s state of mind,” and (6) the “duration of the assistance” given. Id., at 488 (emphasis deleted). Last, Halberstam clarified that those who aid and abet “a tortious act may be liable” not only for the act itself but also “for other reasonably foreseeable acts done in connection with it.” Id., at 484.
Applying that framework, the D. C. Circuit held that Hamilton was liable for aiding and abetting Halberstam’s murder. Id., at 489.[1] The court first determined that Welch had committed a wrong (in killing Halberstam during the burglary) and that Hamilton was generally aware of her role in Welch’s criminal enterprise. Id., at 488. It then explained that Hamilton had given knowing and substantial
- ↑ The D. C. Circuit also held that Hamilton was liable as a co-conspirator. Id., at 489.
