The reversal was based on assertions by Butt, who was convicted of two counts of dealing in materials harmful to minors, that his trial attorney was ineffective for failing to raise a free-speech defense. The high court's opinion agreed that a First Amendment defense would have succeeded.
Daniel Burton, a spokesman for the Utah attorney general's office, said the office is reviewing the opinion.
Butt, now 44, was incarcerated in the San Juan County jail awaiting sentencing on a theft charge when he sent letters in November 2008 to his family, which included notes to his 5-year-old.
In one letter, he sent a hand-scrawled picture of himself naked. In another letter, mailed three days later, he wrote a note to his daughter that said, "Hi beautiful girl. I miss you so much. I can't wait to bite your butt cheek. This is what it will look like. I love you."
The second letter included an even more rudimentary drawing of himself naked and holding his daughter up with her bottom next to his mouth, according to court records. The Supreme Court's opinion says it is unclear whether the picture shows Butt biting his daughter and whether the girl is clothed or naked.
The two letters were intercepted by jail personnel and the family never saw them, court records say. Butt was charged in 7th District Court with two counts of third-degree felony dealing in materials harmful to minors.
Utah law defines "harmful to minors" in part as any description or representation of nudity or sexual conduct that, taken as a whole, appeals to the prurient interest of minors and is "patently offensive to prevailing standards in the adult community as a whole with respect to what is suitable material for minors."
At trial, Butt testified that before he went to jail, he and his daughter had watched a documentary about cave dwellings, which included cave drawings of naked people. The first picture was in response to a request by his daughter to draw himself naked like the cave pictures and the second one was a father-daughter joke, according to Butt.
A jury, however, convicted him on both counts. He was sentenced in July 2009 to up to five years in prison. He was paroled from prison in March 2011.
Butt appealed the convictions to the Utah Supreme Court, where his trial lawyer challenged the sufficiency of the evidence. In a 5-0 decision handed down in June 2012, the justices said the evidence was enough to support the jury's conclusions that Butt "distributed" the material and that the material was "harmful."
The argument that Butt's letters to his daughter contained constitutionally protected speech under the First Amendment was not raised at trial or in the first appeal to the Utah Supreme Court.
In September 2012, attorneys for Butt UCLA law professor Eugene Volokh and Salt Lake City lawyers Troy Booher and Beth Kennedy asked the U.S. Supreme Court to take the case and set a "benchmark precedent" on what material should be considered harmful or obscene as to minors.
The U.S. Supreme Court declined without comment to hear the case. Butt's lawyers then filed a post-conviction relief petition in 7th District Court that alleged ineffective assistance of counsel. Those assertions were based on two grounds: failure to raise a free speech defense and failure to assert a defense based on federal and state constitutional protections of a parent's right to determine what materials are appropriate for his child.
In response, the state agreed the conviction related to the first drawing should be thrown out and conceded the trial lawyer's performance was deficient, according to court documents. The state, however, also argued that the free speech defense lacked merit in regard to the drawing of Butt holding his daughter and said no court has ever expressly adopted parent-child communication as a defense.
Judge Lyle Anderson ruled in favor of the state, and the case again went to the Utah Supreme Court.
This time, the justices sided with Butt, saying they agreed that the drawing was, as a factual matter, "not overtly sexual or sexually suggestive." The ruling concluded that the intended audience Butt's daughter also would not have perceived the picture as sexually suggestive.
The court said that because the conviction was overturned on that basis, it declined to address the parent-child communication argument.
Volokh said the evidence in the case did not fit the allegations against Butt.
"The speech was constitutionally protected," he said, "and was just not a crime in the first instance."