Death investigation with magic??

My husband has been trying to remember the name of a book that he read 10 years ago. He knows he read a paperback version and is pretty sure that the cover is red and black.
He remembers it being about a murder investigation/ death of some sort and people being brought back to life and kept alive by a type of voodoo magic. He thinks it was described as the grandfather of voodoo and the investigators stumbled upon it during their investigation. He thinks it may have had some military elements as well.

Any help or ideas??

He also said it started in New Orleans but definitely led to Africa during the investigation.