LOUISVILLE, Ky. (AP) -- Convicted school shooter Michael Carneal recalled wanting to bring a gun to show-and-tell while in kindergarten, then use the weapon on anyone who didn't like his presentation -- a plot that never came off.

"Of course, I didn't have access to a gun, so it was not realistic," Carneal wrote in an August 2002 letter from prison to a psychologist hired by his lawyers. "But, I do believe that if I had had the means at the time, I would have gone that far."

Prosecutors argue the letter and another written four months later show that Carneal shouldn't be able to appeal his guilty plea to killing three classmates and wounding five others at Heath High School near Paducah on Dec. 1, 1997. They argue in a motion filed Wednesday that if Carneal was aware of his mental illness in 2002, he should have filed an appeal within a year. They say the clock had run out by the time he did attack the guilty plea in 2004.

Carneal's lawyers argue that his plea of guilty but mentally ill shouldn't have been allowed because he was too insane to assist his lawyers and understand the court proceedings when he made the plea.

They say it took years for medications to reduce the severity of his mental illness to the point that he could discuss the hallucinations he was having at the time of the shooting and the plea.

Defense lawyers have said if they can overturn Carneal's plea and sentence, he'll likely spend much of his life in a private mental facility instead of prison.

A federal judge ruled previously that defense attorneys could argue their case at an upcoming hearing because there was enough evidence to show that mental illness stopped Carneal from trying to withdraw his guilty plea sooner. Prosecutors are asking U.S. District Judge Thomas B. Russell to call off the February hearing in their emergency motion Wednesday.

One of Carneal's attorneys, Tim Arnold, said his client's condition has "waxed and waned," preventing him from consistently getting a hold on his delusional structure until long after the letters were written.  "We believe the court should not rely on the diagnosis of the lawyers, but should rely on the testimony of qualified medical professionals in making what will surely be a difficult ruling," Arnold said.

The letters, written to Dewey Cornell, a forensic clinical psychologist and education professor at the University of Virginia, offer a rare look at Carneal, who is serving a life sentence without a chance of parole for at least 25 years for the shootings, which occurred when he was 14. He is eligible for parole in 2023.

Carneal brought a gun to school on the first day after Thanksgiving break in 1997, and opened fire on a group of students holding a prayer meeting.

The Kentucky Supreme Court in 2008 ruled that there wasn't enough independent evidence to sustain Carneal's claims and some of his claims were raised too long after the guilty plea to be considered.

Carneal, now 27 and housed at the Kentucky State Reformatory in LaGrange, wrote the letters to Cornell, who examined him in the years leading up to the appeal in an attempt to determine if the mental illness was hindering Carneal's ability to speak about what led up to the school shooting.

In the letters, Carneal describes feeling "alienated" as far back as kindergarten, with those feelings intensifying over time.  Carneal also tells Cornell that he lied during their interviews for what the inmate thought was his own safety.

Carneal, in the December 2002 letter, wrote that he was on the anti-depressant Zoloft and Geodon, an antipsychotic used to treat schizophrenic patients.

Carneal described his belief in monsters he called "the danes," which he thought would kill him if he told anyone about them. He said he had a "strange psychic ability" that made him aware of the monsters.

Carneal wrote that he was "caught up" in the delusions until 2000 -- even going so far as to persistently rock in chairs so his feet wouldn't touch the ground where the creatures could grab him.  "I still see the people and hands coming out from underneath my bed, but I'm better able to realize that they are not really there," Carneal wrote in December 2002. "I can tell you incident after incident in which I saw, heard, felt, smelt or even tasted things that weren't really there."

Carneal described what happened when he missed medications -- running around in boxer shorts complaining about the cold and imagining plots to attack him.  "I saw a guy with a can opener and thought it was a gun," Carneal wrote. "I started ducking behind the partition."

Carneal wrote to the psychologist that he wasn't trying to make the case for his insanity, and that he just wanted advice on whether he was receiving the proper medication. He acknowledged that the stories of his hallucinations sounded "absurd."

"I am no dummy," Carneal wrote. "I know that you are probably thinking that this is some crazy scheme that I have spent the past five years concocting in order to appeal in court."

Cornell replied in January 2003, encouraging Carneal to stay on his medication and that he was "on the right road" to overcome mental illness.