Harry Potter creator JK Rowling has been cleared by a US court of plagiarising scenes from a little-known children's book.

The Edinburgh-based author was accused of stealing ideas from the late Adrian Jacobs, who died penniless in a London hospice after his own take on boy wizardry, Willy the Wizard, failed to sell in the 1980s.

His estate had claimed Harry Potter and the Goblet of Fire, the fourth instalment in the best-selling series, borrowed the idea of wizards travelling on trains and taking part in a magic contest.

However, New York judge Shira Scheindlin yesterday dismissed the case on the grounds that "no reasonable juror could find a substantial similarity between the two books".

For a start, Jacobs' wizard is a Swiss adult, notable for his beard, hoop earring and "Aladdin-type shoes" and raised by a magical father who "had a contract with God [that] gave him the exclusive monopoly [to perform repairs] on all angel defects", the judge said.

In contrast, Rowling's protagonist was described as a "skinny boy of fourteen with large round glasses, bright green eyes and untidy black hair", raised by non-magical adults.

The judge offered a scathing criticism of the late Jacobs' work, specifically his 1987 book The Adventures of Willy the Wizard – Livid Land. Responding to the case brought by Paul Allen, trustee of Jacobs' estate, she said: "Beyond the background fact of the wizards' contest, the book lacks any cohesive narrative elements that can unify or make sense of its disparate anecdotes – a generous reading may infer that its purpose is to engage a child's attention for a few moments at a time, much like a mobile or cartoon.

"Indeed, the text is enlivened only by the illustrations that accompany it. Livid Land is entirely devoid of a moral message or intellectual depth. It does not present any overarching message or character development."

Because both works are for children, she continued, "the total concept and feel of the works – rather than their plot and character development – is the most important factor for purposes of establishing copyright infringement.

"Here, the contrast … is so stark that any serious comparison of the two strains credulity."

Rowling's US publisher Scholastic said it was "extremely pleased" by the outcome.

"The court's swift dismissal supports our position that the case was completely without merit and that comparing Willy the Wizard to the Harry Potter series was absurd," spokesman Kyle Good said.

Rowling declined to comment personally, but Neil Blair, a partner at the Christopher Little Literary Agency – which represents the 45-year-old writer – said: "We're obviously delighted by the decision."

Despite the US ruling, a similar case in the UK is still live.

In October, the High Court ruled that the claim brought by Mr Allen was "improbable", but could still technically succeed.

Mr Justice Kitchin refused applications by Rowling and her publishers, Bloomsbury, for an immediate dismissal, but ordered Mr Allen to pay money into court as security for costs that may be incurred. Mr Jacobs died three years before Harry Potter and the Goblet of Fire was published.

Rowling's UK lawyer, Gideon Benaim, said after the US judgment: "In relation to the UK proceedings, there is due to be a court hearing in mid-March where the judge will determine what conditions to impose on Paul Allen in return for allowing the 'improbable' case to continue."

Rowling is no stranger to high-profile plagiarism cases.

American author Nancy Stouffer alleged in 1999 that Rowling had copied details from her book The Legend of Rah and the Muggles, published in the mid 1980s.

In Stouffer's work, muggles are small, mythical creatures, whereas in Rowling's world they are non-magical humans.

Stouffer also claimed infringements with her colouring book, Larry Potter and his Best Friend Lilly, but both were thrown out in the US. An American court later fined her for lying in her statements and doctoring evidence to support her claim.

However, Rowling has fallen victim to apparent breaches of copyright herself, pursuing out-of-court claims over Chinese and Indian books such as Harry Potter and Bao Zoulong and Harry Potter in Calcutta.