John Wayne Gacy aka the "Killer Clown" and "Pogo the Clown" was a Des Plaines, Illinois serial killer convicted of 33 murders and who was executed by the state of Illinois via lethal injection on May 10, 1994. 

3 1/2" x 5" photo sent by Gacy to a friend while he was on death row.

The photo shows Gacy dressed as Patches the Clown. 
Gacy has written on the back, Paches the Clown Taken Aug 1, 1977 as seen in "Life" mag Feb, 1979.

John Wayne Gacy Vintage Patches the Clown Photo With Writing