The Downing of Flight PS752: Mistake of Fact and Self-Defence in International Law

By: Rishav Sen and Faizan Ahmad


On 8th January 2020, 176 people lost their lives when Iran shot down Ukraine’s Flight PS752, on the way from Tehran to Kiev. The targeting of Flight PS752 came against the backdrop of increased tensions between the US and Iran. On 3rd January, 2020, the US had engaged in a drone strike against Major General Qassem Soleimani, which was followed by Iran’s retaliatory strike on US assets in Iraq on 8th January, 2020. Anticipating a response from the US, the Iranian Revolutionary Guard Corps (hereinafter ‘IRGC’) moved anti-aircraft missile units to positions around Tehran’s Imam Khomeini Airport (hereinafter ‘Airport’), a civilian airport, without closing it. Instead, the authorities set up a communication channel between the Air Traffic Services (hereinafter ‘ATS’) and the IRGC to ensure that civilian aircrafts were not targeted. On the same day, Flight PS752 took off from the Airport at 02:42:00 UTC. At 02:43:56 UTC, the flight was misidentified as a target by the IRGC. Following a communication failure with the ATS, the IRGC shot it down.

This situation necessitates an assessment of whether a state’s use of force against an ongoing or imminent attack in self-defence can be justified under article 51 of the UN Charter, if it is based on a mistake of fact. In addressing this question, we first analyse the right of self-defence under article 51 and determine whether Iran could take recourse to it without admitting to its mistake of fact. Moving forward, we analyse the state practice on use of force in self-defence due to a mistake of fact. Accordingly, we explore whether state responsibility should be subjected to an objective or subjective standard under such circumstances. Finally, we examine Iran’s jus ad bellum obligations in light of the investigation report by the UN Special Rapporteur and suggest a strict liability rule for determining state responsibility under such circumstances.


Article 51 of the UN Charter permits the use of force in self-defence if an armed attack occurs against a state. For a state to justify its use of force in anticipatory self-defence, its actions must satisfy the elements of necessity and proportionality, which have been recognised in customary international law in the Caroline Case. Therefore, the question which arises here is whether anticipatory self-defence, as interpreted in Caroline, can be read under article 51. Some authors have taken the view that reading anticipatory self-defence under article 51 would be an inappropriate interpretation of the provision which uses the phrase “if an armed attack occurs”. Further, it would defeat the intent behind article 51, which was to minimise the unilateral use of force in international law. However, most authors today recognise the principle of anticipatory self-defence, while placing a high burden of proof on states to satisfy the required elements of necessity and proportionality to prevent its abuse.

Now, there exists a controlling legal principle in international law which advocates that a passenger airliner, whether trespassing intentionally or not, should not be considered a military threat which justifies its destruction. Therefore, notwithstanding the mistake of fact, the mere presence of Flight PS752 in Iran’s airspace would not satisfy the element of necessity and proportionality required under article 51. Nevertheless, it is important to note that the principle of anticipatory self-defence, while highly debated, does not form the focus of this paper. This is because, a mistake of fact allegedly existed in the present case, which led the IRGC to believe that Flight PS752 was a missile heading towards them. Therefore, one needs to determine whether the IRGC’s use of force under such circumstances would be protected under article 51.


A state’s legal responsibility under such circumstances could be determined in three ways: a) An honest mistake of fact would excuse the state; b) An honest and reasonable mistake of fact would excuse the state; and c) No mistake, however honest and reasonable would excuse the state. Herein, an honest and reasonable mistake would exist when a state: a) lacked the required mental element while exercising its use of force; and b) did not take necessary precautions to prevent the mistake of fact from occurring, respectively.

Now, an analysis of state practice shows that a mistake of fact may negate the mental element required for attributing individual criminal responsibility on military personnel. However, for ‘state responsibility’ for jus ad bellum violations, no mens rea (mental element) is required, making it evident that these separate frameworks could respond to mistakes of facts differently. This was made clear in the Dogger Bank incident in 1904. Herein, the Russian Navy opened fire on a British trawler fleet, believing it to be Japanese torpedo boats, due to a mistake of fact. The subsequent Inquiry Commission concluded that the opening of fire in this case was unjustifiable, despite there being no military negligence on part of the Russian fleet commander. Therefore, the Inquiry Commission followed an ‘absolute’ liability principle in attributing legal responsibility to Russia.

Moving forward, on 3rdJuly, 1988, a US naval vessel shot down the Iran Air Flight 655, a civilian aircraft, believing it to be a hostile military aircraft after it ignored repeated radio warnings (the “USS Vincennes case”). Subsequently, the US claimed before the ICJ that it had acted in self-defence since the commanding officer of the USS Vincennes perceived his ship to be under the threat of an imminent attack. The US Department of Defence concluded that the crash could not be attributed to negligent conduct due to an honest and reasonable mistake made by the USS Vincennes. However, a subsequent investigation by the ICAO was silent on whether the mistake of fact in this case was honest and/or reasonable. Instead, it condemned the use of force against a civilian aircraft without prejudice to the provisions of the UN Charter.

Therefore, the position adopted by the Inquiry Commission in the Dogger Bank incident supports the third position wherein the honest and/or reasonable nature of the mistake would not excuse the state. However, the USS Vincennes Case adds to the confusion by not adopting a clear stance on the US’ legal obligations towards Iran. This is further supported by the contradictory stance adopted by different states while debating the state responsibility of the US at the ensuing Security Council meeting.


The USS Vincennes Case shows the difficulty in accepting a state’s self-defence claim based on their alleged honest and reasonable belief. This is because, as held in Nicaragua, state practice must be consistent and there should be opinio juris supporting it in order for it to constitute customary international law.  However, state practice surrounding the mistake of fact defence is inconsistent and opinio juris on this point of law is divided. Therefore, a custom supporting the mistake of fact is yet to form and at best it is ‘emerging’.

Now, under International Humanitarian Law (hereinafter ‘IHL’), an honest mistake of fact which satisfies an objective standard of reasonableness would exclude state responsibility for the use of force. However, under International Human Rights Law (hereinafter ‘IHRL’), the European Court of Human Rights in McCann v. UK excluded state responsibility for the use of force by the state’s agents, when it was based on an honest belief on their part that it was necessary to save lives during a counter-terrorism operation, thus applying a subjective standard in the process.

Nevertheless, the position of law under the UN Charter is clear from the International Court of Justice’s Oil Platforms decision, where it observed that International Law imposes a strict and objective requirement that measures taken in self-defence must be necessary for its intended purpose, leaving no room for any measure of discretion. Accordingly, state responsibility under the UN Charter cannot be excluded due to a mistaken belief which prompted shooting at a civilian aircraft.


Returning to the shooting down of Flight PS752, a recent investigation by the UN Special Rapporteur revealed that Iran had failed to effectively and independently investigate the incident which could have revealed the intentional nature (if any) of the incident. Further, there is no public record of interviews which would help ascertain whether the IRGC honestly believed that Flight PS752 was a missile heading towards them. This raises significant doubts about whether a mistake of fact occurred in the first place during this incident. Moreover, Iran had failed to take necessary precautions to prevent such a mistake from occurring, in the event we accept Iran’s mistake of fact claim at face value. Therefore, Iran’s state responsibility under the UN Charter would be absolute if we adopt the strict liability requirement established in the Oil Platforms decision.

Now, the present case would have contradictory outcomes within the framework of IHL and IHRL. This is because, Iran’s failure to take necessary precautions would not satisfy an objective standard of reasonableness for precluding state responsibility under IHL. However, under IHRL, Iran’s state responsibility would be excluded due to their honest belief that Flight PS752 was a missile heading towards them. Nevertheless, one should adopt the former standard for determining state responsibility since adopting the latter standard would impose an unrealistic burden on an aggrieved party to establish that a state’s belief which led to its use of force was not honestly held.

(Rishav and Faizan are law undergraduates at Jindal Global Law School, Sonipat. The author(s) may be contacted via mail at

Cite as: Rishav Sen and Faizan Ahmad, ‘The Downing of Flight PS752: Mistake of Fact and Self-Defence in International Law’ (The RMLNLU Law Review Blog, 17 August 2021) <>   date of access

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