If Palestine achieves UN "non-member observer status" on Thursday, it could open the door for the International Criminal Court to investigate crimes committed during the decades-long Israel-Palestinian conflict.
While the possibility of swift prosecutions of Israelis is slim, the spectre of such cases being brought before the ICC has overshadowed the Palestinians' bid.
Britain notably said it would abstain from the vote unless the Palestinians pledged not to seek an ICC case against Israelis.
Based in The Hague, the ICC can prosecute those guilty of genocide, war crimes and crimes against humanity, committed since July 1, 2002, when its founding treaty, the Rome Statute, came into force.
So far it has been ratified by 121 countries, although not Israel, or the United States, China and Russia.
Although the court is independent from the United Nations, it collaborates with the global body and only individuals, not states, can be prosecuted before the ICC.
And the court can only pursue an individual if crimes were committed on the territory of a state party -- one that signed and ratified the Rome Statute -- or by a citizen of such a state.
A state party may also refer crimes within the court's jurisdiction to the prosecutor for investigation.
Cases may also be referred by the UN Security Council, as was the case in Libya last year, or the prosecutor can initiate his own investigations with permission from the judges.
For a complaint against Israel however, a Security Council referral is a remote possibility. The United States, Israel's staunchest ally, is a permanent member of the council and frequently uses its veto right in Israel's defence.
The Palestinian Authority has threatened to bring Israel before the ICC if it turns out its late leader Yasser Arafat was poisoned in 2004.
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Already in 2009 it asked the prosecutor's office to investigate alleged war crimes committed by the Israeli military during its December 2008-January 2009 Operation Cast Lead offensive in the Gaza Strip.
The Palestinians recognised the ICC's authority in 2009, something that the Rome Statute nevertheless says only a state can do.
For this reason, former ICC chief prosecutor Luis Moreno-Ocampo decided earlier this year to leave it up to the "competent organs of the United Nations" to decide whether Palestine was a state. If the answer was yes, then at that point the court could decide whether or not to investigate the alleged crimes.
If recognised by the United Nations as a "non-member observer state", Palestine would need to first ratify the Rome Statute or recognise the jurisdiction of the court before trying to bring a case.
If it wins Thursday's UN vote, Palestine's status may no longer be an issue for the court's new chief prosecutor Fatou Bensouda. She may be able to seek approval from the ICC's judges to launch a probe on her own initiative or at the request of the Palestinians.
But Goran Sluiter, international law expert at Amsterdam University, said such a possibility was remote.
"There's a lot of uncertainties," he told AFP.
"Even if they can do it, it's not certain it will lead to a trial."
Even if the ICC launches an investigation, it will need Israel's cooperation to hand over any suspects: the court does not have its own police force.
Senior Palestine Liberation Organisation official Hanan Ashrawi has said leader Mahmud Abbas resisted "intensive pressure" to make concessions on the ICC ahead of the UN vote.
Palestinian envoys have said Abbas will not rush to join the court but could use it if Israel does not change its policies on settlements and other matters.
Israeli foreign ministry spokeswoman Ilana Stein said meanwhile that Israel would most likely not take any punitive measures against the Palestinians for the vote unless they used the upgrade "as a platform for confrontation" at the ICC.