AMARILLO -- A Potter County grand jury has indicted eccentric millionaire Stanley Marsh 3 on charges involving sex with teenagers, according to documents released Thursday.Marsh, 75, was indicted Wednesday on four counts of sexual assault of a child, eight counts of sexual performance by a child and two counts of indecency with a child.Marsh turned himself in at the Potter County jail Thursday afternoon and was released on $100,000 bail.The indictments are "mere allegations," two of Marsh's attorneys, Paul Nugent and Heather Peterson, said in a prepared statement."There should be no premature rush to judgment," the statement said. "Now that we have notice of the specific allegations, we will commence our investigation, which will be thorough and rigorous. We have great faith in our legal system, and welcome the challenge of exposing the truth, and defending our friend and client, Mr. Marsh."The maximum sentence on the most serious charge is 20 years in prison. Special prosecutor Matt Powell said Marsh would be eligible for probation because he has no felony convictions. Powell declined further comment.In February, Marsh's attorneys settled civil lawsuits involving 10 teenagers who said he paid them for sex.Marsh had a serious stroke in 2011 and has also been treated for prostate cancer. His wife is now his legal guardian.Marsh has been free on bond since November when an arrest warrant was issued in cases involving a 15-year-old boy and a 16-year-old.At the time, his lawyers issued a statement noting that the families of the accusers had filed civil suits "seeking millions of dollars" and had waited to come forward with criminal complaints until after Marsh's stroke.The indictments returned this week include four additional accusers who were not part of criminal charges filed in November.Marsh is probably best known for the Cadillac Ranch art installation along Interstate 40 near Amarillo, which features 10 Cadillacs buried nose down. The cars, including a 1948 club coupe and a 1963 sedan, were gathered from junkyards, private collectors and used car lots.This is not his first time in criminal court. In 1998, Marsh pleaded no contest to misdemeanor charges of unlawful restraint and criminal trespassing and served 10 days in jail and paid a $4,000 fine. Prosecutors then dropped five felony charges including kidnapping, aggravated assault with a deadly weapon and indecency with a child.In 1996, Marsh settled a lawsuit with a youth who said Marsh sexually abused him.In the latest case, Powell, who is the Lubbock County district attorney, was appointed special prosecutor after Potter County's district attorney recused himself.In the civil suits, the plaintiffs said they were teens when Marsh gave them cash, alcohol, drugs and, in one case, two BMWs, to have sex with him during secret encounters at his office.