What happened: Last Friday, my colleague Annie Correal reported that inmates at the Metropolitan Detention Center in Brooklyn were being held in freezing cells, in darkness, unable to contact their families or meet with their lawyers.

The story got national attention, as demonstrators massed, inmates pounded at the windows and lawmakers demanded action. Mayor Bill de Blasio sent blankets. Gov. Andrew M. Cuomo called for a Department of Justice investigation. Protesters tried to enter the jail and were driven back with pepper spray.

On Sunday night, electricity and some heat were restored. By then, federal judges were seeking answers.

In a hearing Tuesday, held by Judge Analisa Torres, inmates described the freezing conditions and said problems predated the Jan. 27 electrical fire that jail officials initially said was the source of the problems.

Why it matters: The problems at the M.D.C. come amid a rethinking of criminal justice nationwide, against the backdrop of the Black Lives Matter movement and a groundswell of political activism among Democrats.