Document ID: ./input/supremecourt_opinions/opinions/22pdf/21-1496_d18f.pdf
Page Number: 17.0

Cite as:  598 U. S. ____ (2023) 

11 

Opinion of the Court 

assistance to Welch’s activities by helping him turn his “sto-
len  goods  into  ‘legitimate’  wealth,”  thereby  intending  to
help Welch succeed by performing a function crucial to any 
thief.  Ibid.  And it clarified that Hamilton knew Welch was 
committing  some  sort  of  “personal  property  crime,”  the 
“foreseeable risk” of which was “violence and killing.”  Ibid. 
The court therefore concluded that Hamilton substantially 
helped Welch commit personal property crimes and was li-
able for Halberstam’s death, which was a foreseeable result 
of such crimes.  Ibid. 

That articulation of the common law thus resolved Hal-
berstam.  But Halberstam recognized that the elements and 
factors  it  provided  could  “be  merged  or  articulated  some-
what differently without affecting their basic thrust.”  Id., 
at  478,  n. 8.    It  thus  cautioned—in  a  typical  common-law
fashion—that  its  formulations  should  “not  be  accepted  as 
immutable components.”  Id., at 489.  Rather, Halberstam 
suggested  that  its  framework  should  be  “adapted  as  new 
cases test their usefulness in evaluating vicarious liability.” 
Ibid. 

2 
The  allegations  before  us  today  are  a  far  cry  from  the
facts of Halberstam.  Rather than dealing with a serial bur-
glar and his live-in partner-in-crime, we are faced with in-
ternational terrorist networks and world-spanning internet 
platforms.  By  Halberstam’s  own  lights,  its  precise  three-
element  and  six-factor  test  thus  may  not  be  entirely  ade-
quate to resolve these new facts.  Ibid.  And JASTA itself 
points only to Halberstam’s “framework,” not its facts or its 
exact  phrasings  and  formulations,  as  the  benchmark  for 
aiding and abetting.  §2(a)(5), 130 Stat. 852.  We therefore 
must ascertain the “basic thrust” of Halberstam’s elements 
and determine how to “adap[t]” its framework to the facts
before us today.  See 705 F. 2d, at 478, 489, and n. 8.  To do 
so, we turn to the common law of aiding and abetting upon