Jacobus Dirk (Koos) Hertogs (The Hague, 16 December 1949 – S-Hertogenbosch, 19 July 2015) was a convicted Dutch serial killer.

Police searched his house and found traces of blood matched to Tialda Visser and Emy den Boer.

In 2009 crime reporter Peter R. de Vries started a sting operation, trying to reveal if Hertogs murdered more people or if the claims made in the book were true.

While being filmed with hidden cameras, Hertogs, talking with a 'dear' friend, who turned out to be an infiltrator working for De Vries, made some notable admissions.

In August 2012 writer and psychologist[citation needed] Patrick Oomens published the book De zaak Koos H., in which he questions the claim that Hertogs is a serial killer and concludes that he does not fit the profile.