Officer Wesley Jackson's last stop for the day was a modest white bungalow on a dead-end street cracked dry by the Nevada desert sun. At the front door the policeman confronted a metal security gate and a black and red sign: Keep Out. But even without a warrant, Jackson was free to rifle through the house on the outer reaches of Reno at any time he chose. An elderly man, Joseph Naso – Joe to everyone but the justice system – knew as much as he unlocked the gate and let the officer in.

Jackson went through the routine of saying he was there to do a search under the terms of Naso's probation for theft from a grocery store in neighbouring California. He'd be looking for weapons, drugs, alcohol – anything forbidden by probation conditions. He asked Naso, in his late 70s, if he agreed to the search. The old man knew that if he didn't he'd be off to prison.

Jackson clocked the turmoil and filth. Dirty dishes piled high in the kitchen. Rotting meat lying among other food scattered across the counters. Papers everywhere. The policeman began with the bedrooms. He searched through dresser drawers packed with women's clothing, which seemed odd as there were no signs of anyone else living in the house.

Across the room the officer spotted a pair of mannequin legs turned upside down and fitted with nylon stockings. Naso said he wore women's pantyhose because of a skin condition on his leg. Jackson noted that the old man was wearing socks.

A second bedroom turned up scores of pictures of women naked or dressed only in stockings and high heels. To Jackson, some of the women looked to be unconscious, perhaps dead. Naso later said the photos were taken at a time when "men were men, and women were women".

In the midst of the clutter lay a single sheet of paper with a handwritten list of numbers up to 10. Next to each was the word "Girl" or "Lady" and a location. Naso blustered. Old girlfriends, he said, or models for his photoshoots.

Hundreds more pictures of naked women, who the police estimated ranged in age from 20 to 80, lay about what Naso called his art studio. Another clutch was found in the living room. Some of the women appeared to be posing willingly. Others looked knocked out, or worse. Some were bound with cord. One picture showed a man whose face was turned away from the camera appearing to have sex with an unconscious woman.

Jackson spotted boxes of bullets near a dresser, which was enough to arrest Naso for breach of probation while he continued the search for what he assumed was a weapon hidden somewhere in the house. Days later, the police found a small stash of guns behind a fridge in the garage. But by then detectives weren't talking about Naso's probation violations any more.

A group of officers had descended to search every corner of Naso's house. One of them picked up the aluminium clipboard on the dining room table. He leafed through it, increasingly shocked: the entries amounted to a journal of terror. One said: "Girl in north Buffalo woods. She was real pretty. Front seat of my car. Had to knock her out first. 1958." Another, recorded at about the same time, said: "Salina, Kansas girl I followed and met at Fred Astaire dance studio. She was gorgeous. Great legs in nylons, heels. Had to rape her in my car on a cold wintery night. Snow storm." Page after page of what the police came to call the "rape diary" was filled with similar records of Naso's assaults on women. The diary would come to form a central part of the case against Naso, but there was more.

The search turned up a separate stash of notebooks written years later. If anything, they were even more horrific with graphic descriptions of bondage, torture and murder. Some were apparently accounts of past crimes. Others read more as instruction manuals for the carefully planned and prolonged deaths of individually named women yet to be captured.

Naso's house held another secret. At one end was a room with a bolt on the door that could only be opened from the outside. In the middle of the door was a small flap, of the kind typically found on prison cells so food and other items can be passed through. The window was the only one in the house fitted with metal bars.

Two years after Jackson knocked on his door, Joseph Naso is awaiting trial on charges of murdering four women – all prostitutes, all strangled to death. Those killings are unusual in their own right as they appear to follow the plot of an Agatha Christie novel, The ABC Murders, in which the initial letter of the victims' first and last names were the same.

But the authorities in several US states suspect that's not the half of it. The piles of photographs, notebooks and a string of other evidence discovered in Naso's house point to a serial rapist who attacked women across the United States for more than half a century – and who, in time, graduated to serial murder.

No one dares put a figure on the total number of victims, but Naso is under suspicion for a series of killings from California to New York and Florida as the police believe they have stumbled on a killer who operated so far and wide and over so many years that they didn't know he existed.

Naso's habit of diligently recording every attack has given detectives a bewilderingly large source of leads as they attempt to piece together the picture of his suspected crimes. Added to the diaries and notebooks, the search of his house also turned up driving licences, passports and work identification cards belonging to women – even a birth certificate for someone born in 1914.

The investigation is being led by detectives in Nevada, where Naso was living when he was arrested, but the evidence is taking them across the country, often led by a fragmentary clue which was little more than a reference to a county, a building or a cemetery.

"We think there are others out there we haven't discovered yet," said Chris Perry, director of the Nevada Department of Public Safety. "Typically, when you are talking about a person who has killed more than once, this doesn't stop."

Sheriff Mike Haley established the Nevada task force investigating Naso. "There are probably more. We will pull up every cold case," he said. "The person has travelled around the country, has been engaged with law enforcement across the country." From the "rape diary" the police know something else. If Naso has spent more than half a century committing the appalling crimes the authorities now suspect he is responsible for, there is also evidence he could have been stopped early on. More than once women went to the police to accuse him of sexual assault on them or their daughters. Naso was charged with rape at least twice. But each time he walked away because sex crimes were regarded with indifference, at best, by the authorities of the time. The police on at least one occasion warned Naso to get out of town to avoid arrest.

Naso is older now, but no less belligerent. In a preliminary court appearance earlier this year, shackled and wearing a red and white striped prison uniform, he described the pictures of naked women scattered around his house as his "romancing" and accused prosecutors of misunderstanding his use of the word "rape".

"In my culture, and where I come from, it's a term for making out, scoring, getting to first base," he said. "I use that term loosely" – by which he meant he's from New York.

Everything was done by consent, Naso insisted. Asked how it was that so many women went along with his requests to strip naked and be bound and photographed, he was boastful. "I can probably get half the women in this room to disrobe voluntarily," he said.

At the time Naso began logging his sex attacks in the "rape diary" in the 1950s, he was living in New York. He was resident in the city, but later shifted upstate. In the 1970s he moved across the country to California, settling in the San Francisco area. But Naso's work as a commercial photographer regularly took him back to New York state. In the 1990s he moved on to Nevada, where he was finally captured.

Faced with the mound of leads, detectives focused on the "List of 10". Some of the place names were tracked to an area north of San Francisco. Four of the entries appeared to be references to killings that became known as the "Alphabet Murders" or the "Double Initial Killings" from the late-70s to the early-90s.

The first victim they know of was prostitute Roxene Roggasch. Her body was found in 1977 dumped near Lagunitas, naked with a pair of nylon stockings wrapped tightly around her neck. She appears as the third entry on Naso's list of 10, with the simple reference: "Girl near Loganitas [sic]".

The other victims were also prostitutes found naked and strangled. None were named on the list, but all were tied to it by the places at which they died. Naso has been charged with their murders in part on the basis of DNA evidence found on the stockings used to murder Roggasch. He was also found to be in possession of newspaper articles about the killings of two of the other women.

Attached to the cuttings was a picture of one of the victims in nylons and a garter belt. Detective Richard Brown, who heads the Nevada investigation, said that the photo appears to be of a woman who is already dead. "Her face doesn't appear natural," he said.

There are a further six references on the List of 10 not fully accounted for. One appears linked to the remains of an unidentified woman found murdered in 1983. The authorities still don't know who she is. Another entry makes reference to a "Girl from Miami, down near peninsula" which has had Florida police hunting through unsolved cases. Number seven reads: "Lady from 839 Leavenworth" – the street address of a residence hotel in San Francisco managed by Naso in the 1980s.

Among the piles of notebooks seized at Naso's house were three that went into graphic detail about his intent to torture and murder a woman who lived in the flat above him on Leavenworth, Margaret Prisco. She and her partner called their downstairs neighbour "Crazy Joe" and on one occasion spotted Naso dumping piles of graphic bondage magazines in the rubbish. Eventually they moved to New York and largely forgot about him.

Last year the police called to tell Prisco that among the notebooks found in Naso's house were three dedicated to how he intended to torture and murder her. The details of what Naso planned to do were so horrific that the Nevada detective declined to repeat them to Prisco.

There were other clues to Naso's suspected crimes. As the investigation continued, Naso received a visit at the Washoe County jail from his former wife, Judith. The police monitored the conversation as Naso told her to enlist the help of their eldest son.

"Once Charlie gets into my house, tell him to go straight to my bedroom. In the top drawer of the dresser, under my socks, is a blue two-by-four-inch pouch envelope containing my safe-deposit keys. I've got things in there that are private," Naso said, according to court papers.

In a safety deposit box at a Reno bank detectives found a zippered black bag with an envelope. It contained 66 photographs of women naked or in various states of undress, alongside various identification documents belonging to several women. There was a passport and driving licence in the name of Sara Dylan, a woman who used to be called Renee Shapiro.

Shapiro changed her name to that of Bob Dylan's first wife as an homage to the singer, and was on her way to a Dylan concert 20 years ago when she disappeared. Shapiro had followed Dylan to performances across the US and abroad for years.

"This was her passion in life," said Brown. "That was all she did."

The safety deposit box also held a piece of paper on which Naso wrote: "May 4 1992 Monday pm" – the time of the Dylan concert Shapiro never made it to.

Brown suspects that among the other pictures in the box were those of at least two other dead women who have yet to be identified. They show the victims from the waist down with the discoloured skin characteristic of corpses.

Naso's arrest for the Alphabet Murders near San Francisco shook a community on the other side of the country that had never quite recovered from the killing of three young schoolgirls in the early 1970s.

The murders around Rochester, New York, were dubbed the Alphabet Killings because, again, each of the victims' first and last names shared the same initial. Chillingly, one of the 10-year-old victims in the Rochester area carried the same name as a woman allegedly murdered by Naso in California years later: Carmen Colon.

The families of the dead children have endured one failed investigation after another. One man suspected of the killings committed suicide only to be cleared long after his death by DNA testing. Another suspect, an uncle of one of the murdered girls, also committed suicide and is now thought unlikely to be the murderer.

A third suspect – a former ice-cream vendor in Rochester who later moved to Los Angeles and was convicted of another series of rapes and killings called the Hillside Strangler murders – officially remains a suspect in the Alphabet Killings, but there is only fragmentary circumstantial evidence to connect him to the crimes.

Now Naso has swung into view. He lived in the Rochester area at the time of the girls' deaths and the New York state police describe him as a "person of interest" in a renewed investigation into which they are putting considerable resources.

Yet there are reasons for caution. The only DNA evidence from the New York murders does not match Naso's. They are also very different kinds of victims: schoolgirls in New York, prostitutes in California.

Still, a connection does exist, albeit tenuous. In 1980, a 22-year-old woman named Sheila Shepherd from Saratoga Springs in New York state was found strangled and naked in her bed. Another double-initial killing.

The police made little progress in investigating the murder. There was no suspect and it fell to Shepherd's mother, Marsha Van Ness, to keep the memory of the crime alive, marking it each anniversary. Now the question has arisen: was Shepherd's murder Naso's transition from killing girls to killing women? He was regularly travelling to New York state from California at the time of the murder. Another investigation added to the growing list of Naso's possible crimes.

From the old man's notebooks, detectives believe he drugged, bound and held some of his victims prisoner at his house.

Prosecutors have called Naso's former wife, Judith, who is 73, to give evidence. She told a preliminary hearing earlier this year that her former husband once told her he had given her something to knock her out and that twice in the summer of 1976 she believed she was drugged and sexually assaulted.

On one of the occasions she was at a San Francisco hotel after an evening at a nightclub with her husband. She awoke to find two strange men in her bed who quickly "scurried away". Naso was standing there, watching. "It was almost dreamlike, but it did happen," she said. At another time, she came round in her own bed to find one of her husband's friends lying on top of her. Naso was defending himself at a preliminary hearing earlier this year, so he was allowed to cross-examine witnesses.

He asked his former wife if he had ever physically abused or threatened her, or if she had ever heard of him harming another person. "Well, you did tell me shortly after we married that you were charged with rape," she replied. He shot back: "That was back in the 50s."

Naso was indeed charged with rape more than once in the 1950s, and reported on other occasions. But the prosecutions appear to have gone nowhere and, in some cases, the police barely took the accusations seriously.

Prosecutors have approached a 74-year-old woman who alleged that Naso was the man who raped her when she was a student in Berkeley, California, in 1961. She reported the attack to the police at the time, but said they suggested she was trying to make her boyfriend jealous. According to Naso's own diary, when the mother of one under-age girl he had sex with went to New York police, the officer's response was to warn him to leave town. Perhaps that left Naso with a sense of invincibility as the seriousness of his crimes escalated. Certainly the police missed several opportunities to curb his attacks.

In court, Naso is mostly plodding and matter of fact with detailed handwritten submissions seeking to have evidence suppressed or dismissed. He complains constantly about his treatment.

But when the writings and photographs found in his house are referred to, the old man becomes agitated. At one point he denounced what he called Detective Brown's "obsession" with his photographs and lifestyle, professing outrage at the invasion of privacy of the women in the pictures. "This is my private work, my photography. The women have been violated. What happens in a home is sacred and private. The whole thing is disgusting and I don't see any relevance at all," he said.

During a testy exchange, Naso demanded to know why Brown referred to one of his diaries as a "rape journal". Brown replied: "I call it a rape journal because, in it, you write things such as: 'I had to rape her. I raped her in an alley. I raped her in the front seat of my car.'"

Prosecutors asked to videotape the testimony of one witness at the preliminary hearing because she may not live long enough to testify at the full trial. Betty Matheson is 81 now, living in Florida and very sick.

Two decades ago she had an almost year-long relationship with Naso in which he would ask her to act dead while he photographed her. Naso would also get his lover so drunk she would pass out, and then he'd take more photographs.

In 1992, Matheson returned to Florida and moved in with her son, William. Naso came to visit.

William told investigators that he woke in the middle of the night to hear what he thought was the sound of someone being strangled. It stopped after a while and he went back to sleep. But William asked his mother about it in the morning.

"Joe started strangling me in the middle of the night," she said. Matheson said that Naso wanted to have sex with her while she was unconscious.

At a preliminary court hearing earlier this year, Naso, representing himself again, tried to remind Matheson of what he called "the good times".

"You still look good, Betty, after all these years. You still look good to me," he said. "We had a lot of fun together, didn't we?"

Matheson replied: "Yes" and laughed.

Naso asked: "Did I ever harm you?"

Matheson said she could not recall. "I wish I could remember better," she said.