Barnett, also a deacon in the First Baptist Church, was first elected to the Missouri General Assembly in 1994. He served four terms until 2002, The Kansas City Star said.
In a recent statement, Rice said that "there was insufficient evidence to prove a criminal charge beyond a reasonable doubt.
"The State's witnesses refused to cooperate and invoked their Fifth Amendment privilege to not testify," he added.
Nodaway County Sheriff Darren White told CNN that his office and the prosecuting attorney had been ready to prosecute but did not move forward because the victim and her family refused to cooperate.
"The only people's stories that have been inconsistent throughout this whole thing are the Colemans' -- are the victims in this case -- and I don't know why that is," White said.
Reacting to the lieutenant governor's call for a grand jury review, the sheriff said that his office handled the case "flawlessly."
In an interview with CNN, White described the elder Barnett as someone he had known for more than 30 years. "He's a man that I do consider to be a friend," the sheriff said. But he described as "absolutely shameful" any suggestion that Barnett would have tried to influence the investigation into his grandson.
Melinda Coleman said White had initially told her that other girls had come forward to accuse the same group of boys of similar conduct but changed his story. "He said that they were all liars. I digitally recorded him saying they were all liars and that they just wanted to crucify those poor, innocent boys.
"So my concern is what is it going to take for them to do something here? Is one of these girls going to have to die?" the mother said.
In the weeks that followed her daughter's alleged assault, Coleman said her children received threats. She was also fired from her job as a veterinarian at a clinic. Daughter Daisy is now 16.
The Colemans have since moved from the 12,000-resident town in northwest Missouri, about 100 miles north of Kansas City.
In April, their house in Maryville -- which had been vacant and for sale -- burned. The state fire marshal said that "due to the unsafe nature of the structure, a detailed examination could not be conducted and this fire loss is being listed as undetermined."
A Facebook page campaign called "Justice for Daisy" says a public rally is scheduled for Tuesday at the Nodaway County Courthouse. Protesters will carry daisies in their hands.
"We will increase patrols and do everything in our power to protect our citizens," McDanel said of the protest. "We will remain on high alert."