The parashah of Ki Tetzei contains the largest concentration of mitzvot of any portion. One of these is the basis of the law of negligence. In Torah times, houses had flat roofs which could often be trod upon by animals or people. A parapet would be a simple way of ensuring that no one fell off the roof.
A key element of negligence law is proving a duty of care between the parties involved. What is so novel about this Deuteronomic law is that the Torah recognises any owner of a new house to have a duty of care to ensure the safety of any visitor to that house.
Also, unlike so many of the laws which command against sins of commission, this one actually brings “bloodguilt” on the owner of the house for a sin of omission, thereby widening the scope of obligation that much further.
Maimonides analyses this obligation: “Both the roof and any other object of potential danger, by which it is likely that a person could be fatally injured, require that the owner take action... just as the Torah commands us to make a fence on the roof... And so, too, regarding any obstacle which could cause mortal danger, one, not just the owner, has a positive commandment to remove it.” (Mishneh Torah)
Jewish educator, Aaron Dorfman understands Maimonides to be expanding the obligation even further than acts of omission, to holding every one responsible not just for their own property, but any object of potential danger. He concludes, “When we look at the world, at all the roofs left unguarded, all the dangers that imperil people, the implications are daunting.” Indeed. But Torah, and Jewish tradition, do not absolve us from trying to meet the obligation.