A prosecutor told jurors in his opening statement that a Kansas man added chemicals to gunpowder to increase the explosive power of grenades he was making.

The government outlined its case against Alfred Dutton, of Eureka, in federal court Tuesday in Wichita. The 67-year-old veteran of both the U.S. Army and U.S. Marines is charged with possession of unregistered destructive devices.

His attorney in his opening remarks said his client was working on creating of a mock grenade that he was planning to sell on eBay. He portrayed his client as a tinkerer who was experimenting with also making fireworks.

An explosives expert for the Bureau of Alcohol, Tobacco and Firearms testified about  all the explosive materials and ammunition found during a 2011 search of Dutton’s apartment in Eureka.