“It's later than you think,” reads the tagline for this unblinking study of people who die alone in Los Angeles and those who investigate the mystery of their lives. Winner of the Special Jury Prize at this year's Sundance Film Festival, the film tracks several investigators from the Los Angeles County Coroner's Office as they follow their noses to the stench behind hotel room doors or inside cheap apartments: the decomposing bodies of those who died unnoticed. Using the same chilled formalist rigor to film scenes of Boschian trauma and instances of utter banality-or both simultaneously, as when an investigator desultorily talks on her cell phone while wrapping up a body-directors Blue Hadaegh (a former UC Berkeley student) and Grover Babcock create a mood of uneasy fascination, unironic yet at times wincingly amusing, unsparing yet compassionate. Bringing an Errol Morris aesthetic to James Ellroy country, A Certain Kind of Death speaks of the silent histories of Los Angeles, where unclaimed corpses continue to gather in the shade.