Legitimate Business by Michael Niemann

Ritu Roy, a constable with an all-female United Nations peacekeeping unit in Darfur, Sudan, has been shot dead.  Her superiors call it a random shooting, but her partner, Constable Priya Choudhury, thinks otherwise. She's found a bullet casing from a sniper's rifle, an uncommon weapon in the refugee camp.

The case remains closed until Valentin Vermeulen arrives to conduct a routine audit. As as investigator with the UN, his job is to ferret out fraud... they must expose the players in the not-so-legitimate business of supplying weapons to Sudan, before he becomes the next target.