At tonight's Democratic presidential debate in

Charleston, SC, Sen. Bernie Sanders (D-Vt.) pledged that if elected, deaths while in police custody would trigger an "automatic" federal investigation.

NBC News moderators Lester Holt and Andrea Mitchell presented the candidates with questions from "prominent voices on Youtube." One of these voices, Franchesca Ramsey, who Holt said "tackles racial stereotypes through her videos," asked:

I believe there's a huge conflict of interest when local prosecutors investigate cases of police violence within their own communities. For example, last month, the officers involved in the case of 12- year-old Tamir Rice weren't indicted. How would your presidency ensure that incidents of police violence are investigated and prosecuted fairly?

Holt put the question to Sanders, who replied:

This is a responsibility for the U.S. Justice Department to get involved. Whenever anybody in this country is killed while in police custody, it should automatically trigger a U.S. attorney general's investigation. Second of all, and I speak as a mayor who worked very closely and well with police officers, the vast majority of whom are honest, hard- working people trying to do a difficult job, but let us be clear. If a police officer breaks the law, like any public official, that officer must be held accountable.

It's not clear if Sanders misunderstood the question, was engaging in clever deflection, or was merely tossing out one of his patented throaty calls for drastic reforms that he couldn't possibly have thought of a way to pay for.

Ramsey's question directly referred to "incidents of police violence," but Sanders' answer promised action over deaths "while in police custody." Does that mean after a suspect has been detained? Or did he simply misspeak?

If Sanders was indeed answering the question asked, it is reasonable to infer that he was calling for around 1,000 "automatic" federal investigations a year, based on The Washington Post's unofficial tally of fatalities at the hands of US police forces in 2015.

On The Atlantic's live debate blog, Conor Friedersdorf suggested that "federal funding for hiring special prosecutors at local level [sic] to investigate officer involved shootings is one possibility" for how Sanders' plan could be implemented. An interesting suggestion, as it is hard to imagine how the Justice Department would be able to scrounge up the resources to pursue that kind of a workload without massive staff increases. Either way, you could be sure such a sweeping measure would be met with significant pushback by both police unions and tough-on-crime politicians at every level of government.

Later in his reply to Ramsey, Sanders added, "we have got to de-militarize our police departments so they don't look like occupying armies." This is a welcome statement from a legitimately viable candidate of one of the two major parties (sorry, Rand Paul) and presents a stark contrast with this past week's Republican presidential debate, where the issue of criminal justice reform was completely ignored.

While Sanders' seeming commitment to criminal justice reform is admirable, he underestimates the entrenched opposition to transparency by US law enforcement agencies, the same groups who mostly refuse the FBI's request for them to voluntarily turn over their data pertaining to deadly uses of force.

A less dramatic but far more realistic proclamation would be for Sanders to promise that, as president, he would call for legislation requiring state and local law enforcement agencies to maintain and submit all data pertaining to killings by police, so that we don't have to rely on the news media and volunteers to do the government's job.