After watching a few crime films, I'm wondering how many murders/rapes/kidnappings have been prevented or quickly resolved simply due to the widespread use of cell phones. I'm thinking of the first murder victims in the movie Zodiac, who weren't able to alert anyone of their situation after spotting the suspicious-looking car whose occupant killed them. At the other end of the spectrum, the daughter kidnapped in Taken was found by her father in a fairly timely manner because she had a cell phone and was able to give him details of her kidnappers. So, how significant a role do cell phones play in crime prevention/solving in real life?

—Carly, Chicago

Remember 24, Carly? Highly motivated federal agent Jack Bauer scurries around Los Angeles sticking knives and screwdrivers into terrorists till they tell him where, exactly, they've planted their nuclear bombs, vials of deadly virus, etc.? At one point, the dean of West Point beseeched the show's producers to ease off some on their constant suggestion that torture yields usable intelligence—it seems the troops were getting the wrong idea. All I'm saying: Maybe we shouldn't take our cues on crime-fighting from Hollywood.

Here in the real world, though, we see such cases as the Boston Marathon bombing, where abundant cell-phone documentation of the scene helped investigators quickly locate and release images of the suspects; later, when the soon-to-be infamous Tsarnaev brothers fled in a carjacked SUV, police tracked them via signal from the phone, still inside, belonging to the car's owner. So there are obviously instances in which, yes, cell phones have helped solve crime, and it's not hard to envision scenarios in which they might deter it.

But can we go so far as to say that more phones in pockets actually means fewer victims? Violent crime in the United States has in fact been on a decided decline since the early 1990s—down 51 percent between 1991 and 2015, to the general befuddlement of social scientists, who've attempted to explain the trend with theories ranging from more incarceration to more abortions. Meanwhile, in 1996, people made 55,000 wireless calls to 911; in 2011 it was 396,000. When you see dots like that, it's certainly tempting to connect them.

Unfortunately, the research thus far is pretty thin and tends toward the speculative. The two main sources we've got are these:

A 2012 report out of the University of Pennsylvania's Institute for Law and Economics notes that the beginning of the drop, in the '90s, coincided with the ownership of mobile phones by "more than a trivial share of the U.S. population." Spinning this observation into what they called an "intuition," researchers looked at the relationship between phone ownership by state and reported instances of rape and aggravated sexual assault. These crimes, they reasoned, were—given FBI reporting and classification standards—"likely to occur among strangers and most plausibly deterred by mobile phones." Seeing or assuming that you're carrying a phone, in other words, makes me less likely to assault you. Controlling for a few factors, like per capita spending on corrections and police, the authors found ... well, they found results they called "interesting" and suggested that more work was needed. But they were very encouraging about it.

In 2015, a paper in the Journal of Crime and Justice described research building on those earlier results. The authors broadened the scope of the earlier report—using national-level data—as well as the timeline, looking at the numbers from 1984 through to 2009. And they took into account more categories of crime: seeing a significant negative relationship between cell-phone prevalence and rates of property crime, they noted that, combined with findings from the earlier paper, the data suggest "substantively similar deterrent effects of mobile-phone ownership rates on crime rates." Again, though, identifying association ain't the same as identifying causation, and these guys, too, concluded their paper with a call for further research, larger sample size, better information, etc.

So basically criminologists have looked at your question, done a little research, and come up with: Maybe? It's not hard to see why this is such a complicated case to make. As I mentioned above, theories about why crime is down are basically endless. Another, for instance—called the security hypothesis—suggests that not just cell phones but all manner of advanced tech (car and home alarms, better locks, etc) deserve some credit for falling crime rates. A bit farther out there, others have proposed the crime-substitution hypothesis: social media and gaming have become so popular among young folks that they've simply, um, forgotten to go out and rob people. What with the countless hours postmillennials spend on their devices, it's not just crime they're leaving behind, according to a recent article in the Canadian magazine MacLean's, but all manner of misbehavior: the so-called Generation Z (born since 1995) is "smoking less, graduating more, having fewer pregnancies, and committing fewer robberies, car thefts and murders." Phones do prevent crime, under this theory, but not because we're all calling for help—it's because we're all posting photos of our lunch.

Send questions to Cecil via StraightDope.com or write him c/o Chicago Reader, 350 N. Orleans, Chicago 60654.