Death in Custody Reporting Act of 2011 - Requires states that receive certain criminal justice assistance grants to report to the Attorney General on a quarterly basis certain information regarding the death of any person who is detained, under arrest, in the process of being arrested, en route to incarceration, or incarcerated at a municipal or county jail, state prison, state-run or contracted boot camp prison, state or local contract facility, or other local or state correctional facility. Imposes penalties of up to a 10% reduction of federal Byrne Justice Assistance Grant funding, at the Attorney General's discretion, on states that fail to comply with such reporting requirements. Requires the head of each federal law enforcement agency to report to the Attorney General annually certain information regarding the death of any person who: (1) is detained, under arrest, or or in the process of being arrested by any officer of such agency (or by any state or local law enforcement officer for purposes of a federal law enforcement operation); or (2) is en route to be incarcerated or detained, or is incarcerated or detained, at any federal correctional or pre-trial detention facility located within the United States or any other facility pursuant to a contract with or used by such agency. Requires the Attorney General to study such information and report on means by which it can be used to reduce the number of such deaths.