He also points out that the areas with greater deaths of women and girls appear to correlate to where there have been more media reports of paramilitary, or shabiha, activity. In Homs, Syria Tracker has found, the percentage of women and girls reportedly killed since the start of the war is at nearly 40 percent, compared to the 9 percent average across the country. A woman, in their estimation, is 10 times more likely to die a violent death in Homs than in Damascus.

This violence against women in Homs corresponds to the data we have gathered at the project I direct at the Women's Media Center's Women Under Siege, which is mapping how sexualized violence is being utilized in Syria. Our data show higher levels of sexual assaults in Homs than any other city in Syria, with 35 percent of our total reports taking place there. Also, 70 percent of Syria Tracker's recorded female deaths by beatings and stabbings happened in Homs, the majority in May 2012.

Around 60 percent of Syria Tracker's thousands of reports have at least one video or picture. Over 85 percent have a name of a victim. All have a location of the attack, down to the neighborhood or county. All have an exact date and are corroborated by at least one other source. Over 80 percent of the reports have context about what happened, describing whether an individual death was part of a massacre or something else. Which is to say that this documentation could help toward the assemblage of evidence for potential prosecutions.

Dr. Sandro Galea, chair of Columbia University's Mailman School of Public Health's department of epidemiology, said he considers crowdsourcing like Syria Tracker's an "innovative approach that can be used for surveillance during wars or in unstable situations."

Regardless, this kind of human rights data gathering has amassed its share of criticism, the gist of it being that there is no way to know what portion of the overall violence you're collecting.

"Those reports are important and useful as case studies, but any analysis of that observed data must also take into account what has not been reported -- when and where might violence be happening that is not witnessed by anyone or is witnessed by individuals who do not feel comfortable reporting the violence?" says Megan Price, a statistician with the human rights program at Benetech, a Palo Alto, California-based nonprofit technology organization that has done humanitarian data gathering from Guatemala to East Timor. The data, she says, are more supportive of qualitative conclusions and specific contextual details rather than aggregate conclusions about patterns.

The head of Syria Tracker agrees. "Imagine if after every single massacre you could interview every single person -- that would be great," he says. "But you can't do that." There's bias in the data collection in a statistical sense, he freely admits. Who can get on the Internet? Who then knows about Syria Tracker and feels comfortable using it? But trying to gather reports of killings in a hot war is not about looking for the needle in the haystack. Rather, he says, it is about modeling the haystack. What does the warzone look like? In this case, what does life -- and death -- look like for civilians stuck inside Syria?