Iowa Department of Public Safety
215 East 7th Street
Des Moines, Iowa 50319

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For immediate release: Alex Murphy
  DCI Public Information Officer
Investigative Operations
Iowa Department of Public Safety
March 26, 2014
(515) 443-3014 - cell
(515) 725-6189 - office

Arrest Made in 2009 Sac City Homicide

Orange Park, FLORIDA – On March 25th, 2014, officers with the Sac City, Iowa, Police Department and agents with the Iowa Division of Criminal Investigation interviewed and arrested John David Green, age 54, of Florida, for the June 2009 murder of Sac City resident Mark Koster. 

In the spring of 2010, a missing persons report was filed with the Sac City Police Department by the family of then 58 year-old Mark Koster.  The family believed that Koster had left the Sac City area for a period of time during the summer of 2009, but became concerned when they had not heard from him after several months.  Mark Koster was declared dead in 2011.  In November 2012, his residence was sold and his decomposed body was found concealed in the basement of that residence. 

The on-going investigation into Koster’s disappearance and death led investigators to Green, who had lived with Koster for a short time in 2009.  Green was recently located in the Orlando, Florida, area.  Iowa Investigators worked with the Florida Department of Law Enforcement and the Clay County, Florida, Sheriff’s Office in locating and interviewing Green.  During the course of the interview, Green claimed responsibility for Koster’s death and the concealment of his body. 

John David Green has been charged with one count of 1st degree Murder and is awaiting extradition back to Iowa. 

This investigation was a cooperative effort between the Sac City Police Department, the Iowa Division of Criminal Investigation, the Iowa Division of Intelligence, the Florida Department of Law Enforcement, the Georgia Bureau of Investigation, the North Carolina State Bureau of Investigation, the Clay County, Florida Sheriff’s Office, the Sac County Attorney’s Office and the Iowa Attorney General’s Office.

It should be noted that a criminal charge is only an accusation and all suspects are considered innocent until proven guilty in a court of law.


Media contact:  Iowa DCI SAC Mitch Mortvedt 402.650.7458


Note: A criminal charge is merely an accusation and a defendant is presumed innocent until proven guilty.

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