New York City Police Departments' inadequate training of its officers may give rise to municipal liability if it shows “deliberate indifference” and causes a violation. See City of Canton v Harris, 489 US 658, 389-91 (1978); Bd. of County Comm'rs of Bryan County v Brown, 520 US 397, 403-07 (1997). A pattern of violations is usually necessary to show culpability and causation, but in rare cases, one violation may suffice. Bryan County, 520 US at 409. The Court has hypothesized only one example justifying single-incident liability: a failure to train police officers on using deadly force. See Canton, 489 US at 390 n.10.