The bodies of the two girls were found along the edge of Deer Creek, about three-quarters of a mile from an abandoned railroad bridge where they were dropped off to go hiking.
Police said the suspect has reddish-brown hair, stands between 5-foot-6 and 5-foot-10 (1.7 and 1.8 meters) and weighs between 180 and 220 pounds (82 and 100 kilograms).
More than five months after the disappearance of 14-year-old Liberty German and 13-year-old Abigail Williams, Indiana State Police released a sketch of the suspect in the Delphi murder investigation.
On Monday, they released a sketch showing a more detailed description of what the man may look like.
Investigators are asking the public to study the man's facial features and contact them with any information on him. Delphi girls murdered: What is the evidence? They later released an audio clip of a male voice saying, "Down the hill". Tony Slocum said of Liberty in late February.
Still, despite intense multi-agency investigation by the state police, FBI and others, the man has not been identified by name and no arrests have been made.
The girls were kidnapped and killed near a trail in Delphi.
"It will give people a clearer image of who we are looking for", Riley said.
Police urge anyone with knowledge about the case to contact authorities.
A reward in excess of $230,000 is being offered for information leading to the arrest and conviction of the person responsible for the double homicide.