David C. Hennessy (1858 – October 16, 1890) was an American policeman and detective who served as a police chief of New Orleans from 1888 until his death in 1890.

After the war, during the Reconstruction era, he served with the Metropolitan Police, a New Orleans force under the authority of the governor of Louisiana.

Local white Democrats generally considered the Metropolitan Police as a military occupation army, in part because it protected the right of freedmen to vote, in accordance with the Fifteenth Amendment.

While only a teenager, he caught two adult thieves in the act, beat them with his bare hands, and dragged them to the police station.

With his cousin Michael Hennessy and private detectives James Mooney and John Boland of New York City, he arrested the notorious Italian bandit and fugitive Giuseppe Esposito in 1881.

Esposito was wanted in Italy for kidnapping a British tourist and cutting off his ear, among numerous other crimes.

[3] Hennessy left the department afterwards and joined a private security firm given police powers by the city.

"[5] In 1888, Joseph A. Shakspeare, the nominee of the Young Men's Democratic Association, was elected mayor of New Orleans with Republican support.

[2] Hennessy inherited a police force that was (according to the local press) incompetent and plagued by corruption.

It is likely that the gunmen were wielding sawn-off shotguns (known in Italian terms as lupara): a common type of execution among mafiosi.

According to some reports, Hennessy had been planning to offer new evidence at the trial to clear the Provenzanos and implicate the Matrangas.

[13] Press coverage of the assassination and lynching was sensational and anti-Italian in tone, and generally would not meet modern journalistic standards.