On Tuesday, the Syrian Observatory for Human Rights (SOHR) announced that the war in Syria had reached a grim milestone: Since the conflict began, they had documented the killing of 202,354 people.

And as high as that number is, in a phone call with The Post, SOHR director Rami Abdul Rahman explained it was likely too low. He estimated that 280,000 people had actually died but his group had not been able to verify all the deaths among regime forces or in the Islamic State and Jabhat al-Nusra.

Either way, it's a terrible figure, and significantly up from SOHR's last estimate of 150,000 in April. But this new figure is also a reminder of how little we really know about the death toll in Syria -- and why the figures we do have can become politically controversial.

International bodies have publicly struggled to count the dead in Syria. At the beginning of this year, the United Nations announced it would stop updating its death toll due to concerns about its accuracy (it had last been updated in July 2013, when it stood at 100,000).

"It was always very close to the edge in terms of how much we could guarantee the source material was accurate," Rupert Colville, a spokesman for the U.N. Office of the High Commissioner for Human Rights, told the Associated Press. "And it reached a point where we felt we could no longer cross that line."

In August, UNHCR reversed that decision, and instead released a new report that said that 191,369 had died since the beginning of the conflict until April 2014, in part based on SOHR's figures. Colville then cautioned that the figures were “indicative” rather than “gospel truth."

On Tuesday, Abdul Rahman expressed doubt about the U.N.'s figures, and questioned why there was little detail about those who had died. "If you are collecting everything, then you should should show everything," he said.

Given the scarcity of reliable information from international organizations, activist-run groups like SOHR have filled the void. They are frequently cited in media reports and by government officials, yet outside observers might be surprised at how ad hoc their operation is: SOHR is based in Coventry, Britain, where Abdul Rahman settled when he fled Syria more than a decade ago. While Abdul Rahman coordinates everything from his British base, he says he uses a network in Syria to help collect and corroborate his information. Last year Abdul Rahman told the New York Times that he had four men working from inside Syria and a network of more than 230 activists on the ground.

Abdul Rahman's methods have been criticized by others following the conflict. When the group released its 150,000 figure in April, James Miller, managing editor of the Interpreter and an expert on the Syrian conflict, tweeted a number of disparaging remarks. "Everything about that chart screams BS!" he tweeted at one point, before explaining that he knew "field reporters who have never encountered a SOHR source in Syria."

"There are hundreds, perhaps thousands of examples why [SOHR] is a terrible source," Miller explained in a follow-up email to The Post, before citing a list of his own criticism, including that moderate rebels were listed as civilians in the data – an apparent change to the methodology that was also noted by Micah Zenko at the Council of Foreign Relations. Miller argued that the way SOHR broke down their numbers between civilians and jihadists showed that they were "significantly less objective" than other groups tracking data, though he added that their bias was unclear.

Abdul Rahman is generally perceived to be in opposition to Bashar al-Assad's Syrian regime, but at times the motivation behind SOHR can seem more complex. Recently, the organization began drawing attention to what it said were civilian deaths created by U.S. airstrikes. That created an awkward situation for the United States, which had frequently cited the organization's statistics. "Nobody is happy with our work, because nobody wants the truth to come out," Abdul Rahman told the Huffington Post in November. "Our group doesn't have the whole truth, but we are very close."

Perhaps the most common criticism of SOHR is that it doesn't share its data or methodology, meaning that it is difficult, if not impossible, to check. There is not much to check it against, anyway: The next most prominent group counting the number of deaths in Syria is the Violations Documenting Center (VDC). "They basically endeavor to have more than one activist in a location, and the activists are not in touch," Lama Fakih of Human Rights Watch told the New Republic approvingly last year. "They collect info separately, and they use that separate analysis to corroborate the info they’re receiving.”

VDC's website currently estimates that 108,679 "revolutionary martyrs" have been killed. Bassam al-Ahmad, a spokesperson for the VDC, told The Post earlier this year that SOHR's numbers seem realistic, but their own methods for confirming the dead are relatively strict (for example, they only count those whose names they can confirm) and thus skew lower.

Counting the dead in any conflict is difficult. Estimates for the number of dead in the Iraq war can range between 110,937 (on the low end of the Iraq Body Count project estimate) to 655,000 (from an especially controversial 2006 Lancet study), and the methodologies of estimates can be political – one recent report suggested that the death tolls from the Democratic Republic of Congo (DRC) and the Darfur conflict were deliberately exaggerated. Such discrepancies are hardly a new phenomenon: Estimates for the number of Germans who died in World War II can vary between 4 million and 5.3 million, for example.

"I think in a way social media has raised some people's expectations when it come to verifying deaths," Eliot Higgins, a British blogger who has tracked the war under the name Moses Brown, wrote in an email. "With so many deaths shown in pictures and videos, it seems some people are unwilling just to accept numbers any more, they want videos of corpses before they'll accept anything. It sort of creates an unrealistic expectation of what's required to verify a death in a conflict like Syria, and really people will believe the figures they want to believe."

There still remains hope that one day people in Syria will face trial for war crimes, however, and evidence on deaths collected by SOHR and other groups may prove important. Sadly, it appears that there are few critics who think SOHR's estimates are too low. Some think they should be higher.