This week, the country was shocked at the story of a group of teens who watched a man drown in a pond, and did nothing to help, not even call 911.

Cell phone video from one of the teens, who filmed the incident, showed Jamel Dunn struggling to stay afloat, while the five boys laughed, cursed, and jeered at him. At no point did any of the teens make any effort to help the 32-year-old man or alert authorities, and even after his death, they didn't notify police. It took three days for Dunn's family to report him missing, and another two days for his body to be found.

Detectives investigating Dunn's death identified and questioned the boys, but had to release them, as under Florida law, they did nothing wrong and had no requirement to render any kind of aid to Dunn.

While all 50 states have Good Samaritan laws that legally protect both medical personnel and bystanders who render assistance, only about ten states have laws that require such assistance be given, either through physical rescue or calling first responders. What's more, these laws usually carry nominal penalties, and are rarely, if ever, used to prosecute.

While it's easy to see a case like Dunn's and declare "there ought to be a law," according to Georgetown law professor David Hyman, there are good reasons that more states don't have duty to rescue laws.

"In my view, imposing an obligation to notify a professional rescuer is much more defensible than imposing a duty to assist, because you don't want the rescuer to end up dead as well," Hyman told ATTN:.

Hyman is an expert in the history and application of duty to rescue laws, having authored one of the only authoritative legal studies on these incidents, the 2006 paper, "Rescue Without Law: An Empirical Perspective on the Duty to Rescue." Despite non-rescue cases getting outsize attention, Hyman wrote that "proven cases of non-rescues are extraordinarily rare, and proven cases of rescues are exceedingly common — often in hazardous circumstances, where a duty to rescue would not apply."

In speaking to ATTN: about the Dunn case, Hyman emphasized that the boys not calling first responders was indefensible, but that they had no moral duty to put themselves in danger to try to save Dunn.

"[The Florida case] is shocking because of the bad behavior of the people involved, but going into the water to rescue this person was quite dangerous," he said. "You don't know how deep the pond is, you don't know how he's going to struggle."

In his paper, Hyman cites a number of cases where someone trying to rescue a drowning victim also drowns. Sometimes, more than one rescuer drowns trying to save the same person. Possibly the most shocking finding of the paper is that "proven rescuer deaths outnumber proven deaths from non-rescue by approximately 70:1."

In a different article, lawyers Hayes Hunt and Thomas M. O’Rourke wrote about another prominent non-rescue, when New Yorker Ki Suk Han was pushed onto the tracks at Times Square and was hit by a train. In that instance, a freelance photographer snapped a picture of Han seconds away from death, but made no effort to rescue. The photographer wasn't legally punished, though, as New York has no duty to rescue laws, and, even so, trying to rescue Han would have put the photographer in mortal danger.

"Even established duty to rescue laws are carefully crafted in a way that mandates rescue only if there's no risk or inconvenience to yourself," Hyman said.

In speaking to CNN, Cocoa Police Department spokeswoman Yvonne Martinez made it clear that even without a duty to rescue, the boys should have called first responders. “It’s one thing to see something and not want to put yourself at risk," she told the cable network. "But to not call anybody, to sit there and to laugh and humiliate this person is beyond my comprehension.”

While no existing duty to rescue law would have required the boys in Florida to put their lives at risk to rescue Dunn, several other states have "duty to inform" laws, that mandate calling first responders. But even these laws exist in only a few states, and carry minor penalties.

"The default in Anglo-American law is that people have no duty to assist one another," Hyman said. "So enacting legislation requires things to happen that motivate a state to change that default." In rare cases, these incidents spur states to pass laws requiring assistance in some way, such as Nevada passing a duty to inform law after a teenager watched his friend rape and murder a small child.

Hyman found that these duty to inform laws fit well into existing legal framework, but that even if Florida did have such a law, the boys are minors, and would have faced only minor penalties anyway.

So while non-rescuers are pilloried in the court of public opinion (with very good reason, in the case of Dunn's drowning), such incidents are rare, and there's no moral or legal duty to face death to save someone else from death. Most of the time, Hyman found, people attempt it anyway, without a legal requirement to do so.