Mistake of fact in killing due to mistaken identity?

A police officer is currently facing a complaint for homicide for killing a man whom the cop thought was a robber.

INQUIRER REPORTS: A complaint for homicide was filed on Monday against a policeman accused of shooting and killing a 29-year-old construction worker he allegedly mistook for a robber in Santa Rita town, Pampanga province. The victim, Federico Pineda, had just celebrated his 7-year-old daughter’s birthday and was bringing an uncle home on his motorcycle when he was chased by Pat. Eframe Ramirez at 10:30 p.m. on Jan. 2. Police said Pineda, who was in a white undershirt, was shot in the back but managed to run to his in-law’s house where he died. His wife, Carla, filed the complaint against the policeman in the provincial prosecutor’s office here. (Read more: Tonette Orejas - @ttorejasINQ. Philippine Daily Inquirer. January 05, 2021. "Homicide rap filed vs Pampanga cop who shot man mistaken for robber." newsinfo.inquirer.net/1379428/homicide-rap-filed-vs-pampanga-cop-who-shot-man-mistaken-for-robber)

Reynold Villania, a lawyer-cop famous for his enlightening and educational posts about police procedures and legal issues, posted the following discussion about this. He warns police officers that the common expression "better kill than be killed" should be abandoned or revisited and revised as "better kill if allowed by law than be killed."
Let this incident be a fair warning to all of us. Mistaken identity is not a ground for us not to incur criminal liability. That one cannot just use his firearm against a fleeing suspect if the latter did not pose imminent or actual danger on one's life." (Read more: Reynold Villania, 2021. Napagkamalang magnanakaw. www.facebook.com/1593763074223416) 
Hindi natin puwedeng barilin ang tumatakas na suspek, lalong lalo na kung hindi naman nanlalaban. Ibang usapan kung prisonero. [We police officers cannot legally shoot a fleeing suspect, especially if there is no unlawful aggression. Of course, the discussion would be different for escapees.] 
Anong nangyari sa pulis dito? Kinasuhan na ng homicide, isang mabigat na kaso, sibak pa sa serbisyo. Makalusot man sa kriminal at hindi makulong, siguradong walang trabahong babalikan. Mabigat na problemang haharapin ngayong bagong taon. [What happened here? The police officer who shot the victim is not only facing criminal charges for homicide but also loss of employment in the government service. Even if he gets acquitted in the criminal case, he surely can no longer expect to get his job back. This is too heavy a problem to face just when the year is starting.]
MINSAN, HINDI TOTOO NA MABUTI NA ANG MAKAPATAY, KAYSA SA MAPATAY. Kulang. Dapat, MAS MAGANDA KUNG MAKAPATAY (AYON SA BATAS), KAYSA SA MAPATAY. Pagbinaliwala ang libro at pinairal lang ang lakas, may kalalagyan, sira at damay pa ang organisasyon. Explaining to the max na naman ang pamunuan. [IT IS NOT CORRECT TO SAY: BETTER KILL THEN BE KILLED. It should be: BETTER KILL IN ACCORDANCE WITH LAW THAN BE KILLED. When the law is disregarded and rationality gives way to brute force, the organization -- the Philippine National Police or PNP --  is dragged down. Leadership's time and energy would be wasted on explanations.] 
Hindi bawal ang gumamit ng puwersa o baril. Hindi bawal ang makapatay ng tao, pero dapat nasa libro. [The law does not prohibit the use of force or gun per se. The law does not prohibit the killing of a person as long as under circumstances which the law allows.] (Read more: Reynold Villania, 2021. Napagkamalang magnanakaw. www.facebook.com/1593763074223416)

The applicable law here is mistake of fact. Is mistake of fact a defense in this case? The answer is no. For mistake of fact to successfully exculpate an offender, the circumstances should be that the act would have been legal and justified, had the facts been as the offender thought they were, exercising due care as required by the circumstances, exercising a lawful right and having good faith.

The above is the teaching of the Supreme Court in US v. Ah Chong wherein the accused was acquitted for striking a fatal blow that killed his roommate because circumstances made him believe that there was unlawful aggression. The High Court explained:

A careful examination of the facts as disclosed in the case at bar convinces us that the defendant Chinaman struck the fatal blow alleged in the information in the firm belief that the intruder who forced open the door of his sleeping room was a thief, from whose assault he was in imminent peril, both of his life and of his property and of the property committed to his charge; that in view of all the circumstances, as they must have presented themselves to the defendant at the time, he acted in good faith, without malice, or criminal intent, in the belief that he was doing no more than exercising his legitimate right of self-defense; that had the facts been as he believed them to be he would have been wholly exempt from criminal liability on account of his act; and that he cannot be said to have been guilty of negligence or recklessness or even carelessness in falling into his mistake as to the facts, or in the means adopted by him to defend himself from the imminent danger which he believe threatened his person and his property and the property under his charge. (G.R. No. 5272, March 19, 1910)

This is different from the case of the policeman who shot a man he thought was a robber. There was no justification at all for the shooting that resulted in the construction worker's death, even if it were true that he was a fleeing suspect. In other words, there is no valid reason under the law to shoot a suspect even if he truly were the robber the policeman mistook him for.