From 2011, Danielle Bremner travelled the globe with her partner, Jim Clay Harper, after the pair fled the US while on probation for graffiti-related offences. They painted as Utah and Ether and were dubbed the Bonnie and Clyde of world graffiti.

But Harper was jailed for six months on Tuesday, his sojourn having come to an end in a headlock on Brunswick Street when Luke*, a single father from Fitzroy, confronted him about defacing shops.

Ms Bremner and an Australian graffitist, who tags as Nokier and was with Harper the day he was arrested, were tracked across the country for almost four weeks by the Victoria Police transit safety divisional response unit. When the pair checked in online for a flight due to arrive in Melbourne on Monday, police were waiting at the airport.

But Nokier and Ms Bremner instead flew to Hong Kong. It is understood police were unable to prevent them from travelling internationally because the offences they are suspected of committing were not serious enough to warrant their passports being cancelled.

Shortly after he was arrested on May 4, police found that Harper had extensive travel plans in Australia. It was also discovered that Ms Bremner and Nokier would be joining him on the tour.

Nokier was wanted by police for allegedly also assaulting Luke and, along with Harper and Ms Bremner, painting trains and other sites across Melbourne.

Nokier fled Brunswick Street after Harper was arrested, and soon went interstate with Ms Bremner.

Police had not known Nokier's real name until shortly after Harper's arrest. His identity has not been made public, but he previously painted with the duo as they travelled throughout Europe, Africa and Asia on what they called a "probation vacation".

Nokier features in a video taken in Tunisia and is credited with taking photos of the pair in India. The material features on websites and social media accounts seemingly managed by the couple or their peers, which feature online stores and details about upcoming releases and exhibitions.

Police are often tipped off by international authorities about "spraycationers" before they depart on flights to Melbourne, but are understood to have received no such warning about the pair when they arrived from the United Arab Emirates on April 21, as it had been almost five years since they fled the US and authorities there had not tracked them.

Acting Inspector Dave Cochrane, of the transit safety divisional response unit, said 18 interstate and international graffitists had been charged in Victoria in the past three years.

"Unfortunately, international and interstate graffiti vandals come to our state to break our laws, vandalise our property and disrupt our train services. They cost us a lot of money in clean-up expenses and make our city an eyesore.

"Our message to these offenders is that we will not tolerate this behaviour, and there are consequences when you are prosecuted.

"We have a strong intelligence network and investigative capability, which means we know who you are and why you are entering our state."

Harper and Ms Bremner are said to have started painting in Melbourne with Nokier three days after arriving. It is alleged they tagged trains in Bayswater, South Kensington, Pakenham and Traralgon.

Harper, a 31-year-old from Chicago, pleaded guilty to offences including assault and criminal damage. He will be deported after his sentence and is likely to spend six months in Rikers Island prison in New York for breaching his probation.

Bremner is a 34-year-old former Fashion Institute of Technology student from New York.

In 2008, the pair returned to the US from Europe and were charged with tagging trains over the previous three years. They were to have been on probation for five years after their release.

"Even being in possession of basic art materials like paint or markers would have been in violation of our probation," the couple told website The Hundreds early last year.

"We decided that we just couldn't live like that, putting our lives on hold for five years. We knew we wanted to go somewhere new, somewhere we hadn't been before and somewhere where there were lots of walls, trains and metros to paint."

By now, their probation would almost have ended.

"When we got out, we knew that we wouldn't stop painting," they said.

"Who knows, maybe you'll see our names rolling up to a train station in your city sometime soon."

Harper's name is unlikely to be seen rolling anywhere for a year, other than a prison wall.

He and Ms Bremner never planned on going home. Now, it appears, neither does Nokier. As a graffitist, he is Bonnie's new Clyde.

* Not his real name