The family is now suing King County, and on Wednesday insisted the driver who caused the crash needs to testify but can't because the prosecutor's office is standing in the way.
Ann Deutscher and Jim Dore are the attorneys suing over the deadly 2008 crash, when a 16-year old driver lost control on Green River Road and slid backwards into the icy Green River.
The driver's 2-year old cousin Hunter and 13-year old stepbrother Austin were killed. Austin's body was never found.
Police and court documents reveal there was no evidence to criminally charge her.
"No evidence of drugs, speed or negligence on her part," Deutscher said.
But the attorneys believe King County is at fault in the crash because a section of the road was unsafe at the time of the accident.
"This is a minor accident if she would have just hit a guard rail," Dore said. "There would not be any dead children."
Dore said there was no guardrail and alleges the road was too narrow.
The lawyers insist they need the driver -- the only living witness -- to testify. But unless she is granted immunity, Deutscher said she will have to plead the Fifth Amendment because in Washington, there is no statute of limitations on vehicular homicide.
"It tells the jury whether you are guilty or not if you are forced to take the Fifth Amendment," Deutscher said. "Any reasonable citizen is going to take an inference that she is guilty."
The Prosecutor's Office declined to be interviewed because litigation is pending, but in a statement said they concluded there was insufficient evidence to support vehicular homicide charges. Officials also said declining to file a criminal case does not confer immunity, adding immunity is "an extremely rare exercise of power."
The lawyers filed a motion with the courts asking a judge to intervene in the issue. A hearing is set for July 29.