Aside from the terrible human cost, there’s a critically important lesson in Iran’s downing of Ukraine flight PS752 over Tehran — namely, that the Iranian regime is led by pathological liars.

The accident itself seems to have been the result of a poorly trained air defense unit and frayed nerves. Seemingly out of contact with civilian air traffic controllers, the missile unit may have thought that flight PS752's post-takeoff radar contact was actually an intermittent track on a stealth bomber. Perhaps they assumed this was America's response to Iran’s missile strikes on U.S. forces in Iraq. But if the downing itself was an accident, Iran’s response to it was anything but. On the contrary, we now know it to have been a galling example of willful deception.

Even as the evidence of a missile impact has become clear, Iran has continued to lie. An Iranian spokesman described accusations of Iranian involvement as lies reflecting poorly on those "engaging in psychological warfare." Foreign Minister Javad Zarif has been speaking with Canadian and Ukrainian foreign ministers but admits nothing. President Hassan Rouhani has said nothing. And Iran has acted to scrub the wreckage of incriminatory evidence.

Such deception tells us everything about the regime's defining arrogance and disregard for the truth. After all, Iran’s leadership must have assumed that someone would figure out the actual cause of the crash. Iran is well aware that the U.S. intelligence community pays a close eye to its missile systems and military communications. That should have given Tehran cause to pause before jumping into lies. You might also have thought Tehran would consider the risk that foreign diplomats had heard the missile impact event and noticed flaming debris falling to the Earth.

But Iran’s leaders simply didn’t care.

They didn’t care because to care would be to admit the truth, and to admit the truth would be to show humility. And that’s something they simply can’t do. The rot starts at the top. Supreme Leader Ayatollah Ali Khamenei is presented as a humble servant of the people under Shia Islam. But he’s actually a geriatric cretin drenched in the blood of innocent Muslims. Surrounding himself with sycophantic hard-liners, and then providing those hard-liners with access to lucrative industries, Khamenei has ensured that his elites hold to a wholly exclusionary world view: they alone must come first every time.

It’s harder to explain why Rouhani and Zarif lied. While they have few moral scruples, these more-moderate elements of the regime recognize that Iranian deception on matters where Iran is likely to get caught does far more harm than good. Perhaps they were directed by Khamenei to lie. More likely, they assumed their lying was the easiest course of action. That if they got away with it, great. If they got caught, they could deny responsibility in confidence that China, Russia, and the European Union would ultimately choose to ignore it.

But the result is the same. The full spectrum of Iran’s top leadership has shown utter disdain for the destruction of 176 innocent lives. One obvious conclusion follows.

If new nuclear negotiations begin, we should demand a tougher inspections regime than that which John Kerry established.