The verdict by a Federal Court jury in New York comes on the heels of a judgement in September 2014 that the Arab Bank knowingly supported terrorism because funds transfers it made amounted to material support for Hamas, a designated terrorist group.  A further hearing, scheduled for May, will fix the bank's penalty, which some legal observers warn could be as much as $US1 billion.

The verdicts rely on a 1980s precedent created after a slip-up by a usually meticulous Washington burglar, whose operation was so smooth that "his" and "hers" Mercedes Benzes were parked in the driveway of his $US1 million home in well-heeled Great Falls, Virginia.

While robbing a Washington DC home on the evening of December 5, 1980, Bernard Welch fired two shots from a revolver when he was interrupted by the arrival of the homeowner, noted cardiologist and author Michael Halberstam.

Halberstam took both shots in the chest but managed to get himself into his car and while attempting to drive himself to hospital, saw the fleeing Welch and ran him down, knocking him unconscious – which is how police found him. Halberstam, however, lost control of his car, crashed into a tree and, just hours later, died in a hospital operating theatre.

Halberstam's widow, Elliott Jones, sued the convicted and jailed Welch. But she also roped in Welch's partner and bookkeeper Linda Hamilton, on the novel legal grounds that she had knowingly lived off the earnings of Welch's crimes. Much to the surprise of legal experts, the court agreed and Hamilton was ordered to pay the widow $US5.7 million.

That ruling underpinned the first civil action against Hamas fundraisers in the US, which in 2004 saw $US52 million in damages awarded against the Holy Land Foundation over the killing of 17-year-old Brooklyn-born David Boim at a bus stop near Jerusalem. Under a 1992 statute passed after the killing of 69-year-old, wheelchair-bound Leon Klinghoffer, who was shot and thrown overboard from a Mediterranean cruise liner hijacked by Palestinian gunmen, the damages in the Boim verdict were then tripled to $US156 million.

Before the Boim case there had been two civil verdicts against Hamas, amounting to about $US300 million, but getting Hamas to pay was close to impossible. So lawyers started to seek defendants who could be brought before US courts – or who had funds or assets within the reach of the US legal system.

And so the Palestinian Authority and the PLO found themselves in the same Welch-Klinghoffer pincer grip as Monday's decision was delivered in New York. The Palestinian leadership was held responsible for six attacks between 2002 and 2004 in which 33 US and Israeli citizens died and 400 more were wounded.

Mounted by the Israel Law Centre, or Shurat HaDin - which according to a US government cable released by WikiLeaks, works closely with Israeli intelligence - the case was taken on behalf of 10 plaintiff families.

"The PLO now knows that there is a price to be paid for sending suicide bombers into our cafes and into our malls," Shurat HaDin founder Nitsana Darshan-Leitner told Foreign Affairs magazine.

The Palestinian Authority said in a statement that it would appeal. In previous terrorism cases, the Iranian and Libyan governments have been able to claim "sovereign immunity", but the PA and the PLO were exposed because Washington does not recognise a Palestinian state – and in this case, neither did the court.

The verdict coincides with US warnings that the Palestinian Authority is on the verge of financial collapse; and as Israel withholds more than $US100 million a month in tax revenues it collects for the Palestinians, in retaliation for the PA's decision to seek membership of the International Criminal Court.

The irony of the PA and the PLO taking such a hit, when they are the entities that the US funds and Israel supports to provide security for Israel within the now-comatose peace process begun by the Oslo accords of the 1990s, will not be lost on many in the diplomatic community.

Attorney Kent Yalowitz told reporters that Shurat HaDin would pursue the assets of both Palestinian entities, including bank accounts, securities and real estate. Ms Darshan-Leitner said that they would also pursue the Palestinian tax revenues held by Israel.

The case turned on arguments that the PA and the PLO had enabled and encouraged the bombers. The defence insisted they had acted alone.

The plaintiffs argued that many involved in planning and executing the attacks had worked for the PA, which had paid salaries to terrorists jailed in Israel and had made "martyr payments" to the families of suicide bombers.