Story highlights Geoffrey Portway pleaded guilty in May to child porn and solicitation to commit violence

Prosecutors say he planned to kidnap, rape and eat children

His defense lawyer says Portway "lived in a fantasy world" and did not harm children

Portway is scheduled to be sentenced Tuesday

The Boston-area man who planned to kidnap children, rape and eat them is awaiting sentencing Tuesday and is seeking a prison term of 18 years followed by lifetime supervised release, according to court documents.

Geoffrey Portway, 40, who pleaded guilty in May to distribution and possession of child pornography and solicitation to commit a crime of violence, submitted a document through his attorney to Massachusetts District Court on Friday, providing information to be used in imposing a sentence "sufficient but not greater than necessary," the court document says.

The document includes background on the case, cites similar cases, and reasons for why Portway agrees to a term of 18 years, with a maximum of 21 years and 10 months. Such reasons included the contention that he "never engaged in inappropriate sexual conduct with a minor," that Portway will be required to register as a sex offender upon his release, limiting his future employment options, and there was "no evidence that (Portway) ever acted out any of his fantasies."

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Portway, a former computer operator, also agreed to pay $10,000 in restitution fees.

Federal authorities are recommending that he go to prison for at least 27 years, according to other court documents filed last week.

"Portway has pled guilty to some of the most vile and heinous crimes known to our society," federal prosecutors wrote in a sentencing recommendation.

But a lawyer for the 40-year-old defendant told CNN his client "lived in a fantasy world" and there was no evidence he harmed any child.

After his arrest, Portway underwent mental health evaluations requested by his attorney, who referred him to a clinical and forensic psychologist who assessed Portway's "risk for re-offending and the degree of danger he posed to the community," according to court-filed mental health evaluation documents.

The documents describe a troubled childhood. His parents divorced when he was young, and Portman realized he was gay when he was 8 years old but was afraid to reveal it because his father was homophobic, the evaluating psychologist Dr. Eric L. Brown, wrote. Around the same time, according to the evaluation, he became increasingly fascinated with children's tales such as "Hansel and Gretel," in which two children are caged and fattened up so that a witch can eat them.

Portway had a "wish to be eaten" that "fulfilled a more basic desire to be wanted, valued, and incorporated by another person," wrote Dr. Brown.

When Portway's home in Worcester was searched last year, authorities found tens of thousands of computer images and videos of child pornography and 4,500 exchanges of child pornography between Portway and the people he chatted with online. The images included children purportedly being cooked and prepared to be eaten, court documents said. Those photographs are sealed.

Authorities also found a locked basement, court documents show. Photos taken the day of Portway's arrest, and released by prosecutors, show a narrow wooden staircase leading downstairs to a soundproof room.

It was furnished with a metal cage with a circular hole for feeding, a rusted and worn steel-topped table, as well as multiple kinds of metal bondage equipment. A child-sized coffin made of plywood was found on the floor nearby.

Portway's lawyer, Richard J. Sweeney, told CNN that his client's sentencing hearing will be "the proper time to address all the issues addressed by the government." But he added, "There's no evidence at all of Geoffrey being involved with any child or harming any child."

"Geoffrey lived in a fantasy world where he did live-action role playing, did things online unrelated to child porn and cannibalism. A lot of the chats that he had were, in his mind, fantasy," Sweeney said. "When they went out to the other people he was talking to, these other people actually had kids they were taking photos of. Geoffrey did not have any kids he had abducted, though he certainly talked about it."

Photographs reviewed by CNN show handcuffs, rope intended for bondage, bleach, disposable scalpels and syringes, mouth gags, a butcher kit with multiple knives, a child-sized red "onesie," and castration tools. His DVD collection, documents show, included titles such as "Hansel and Gretel," "The Real Cannibal Holocaust," "The Genesis Children," and "Cannibal Ferox," a film with the tagline "Make them die slowly."

Online chats, seized by police, showed Portway called his basement a "dungeon" where he intended to "keep kidnapped children while he sexually abused them and as a place to eventually murder and cannibalize the children."