There are more than 800 surveillance towers located along U.S. borders, a number that is expected to triple in the next decade. These towers, according to a government accountability report, “detect items of interest, such as people.” But interest can be fickle. As part of “Dying on Camera,” a sprawling package of features co-published by the MIT Technology Review and Times of San Diego, Lillian Perlmutter reports on the death of Graciela Gómez Hernández, one among hundreds of migrants whose final moments seem as though they should have been witnessed. “The proximity of so many deaths to high-resolution cameras leaves two distinct possibilities,” Perlmutter writes. “Either the system didn’t detect these people in distress, or it did detect them—and officials offered no response. “

Surveillance towers have proliferated in recent years, as contractors added newer camera systems that use artificial intelligence to distinguish border-crossers from other people and animals, and track their movements, at an overall cost of more than a billion dollars. Yet as the cameras scan the terrain, migrants continue to die in plain sight.