The light walls of Nina Gross’s west London home are filled with artworks paying tribute to her sister Alice, who was murdered in 2014.

Gross, 24, an artist and upholsterer, says that creative endeavours are the only means by which she can find a way through her grief about the loss of her sister at the age of 14.

Alice was murdered by Arnis Zalkalns, a Latvian man who lived in the UK and had murdered his wife but whose criminal record did not emerge before he killed Alice.

While Nina’s art helps her to process her own loss, she says she fears that the UK’s exit from the EU could risk more families finding themselves in the same position.

Five years after Alice’s death, Gross is giving her first interview to warn that the loss of access to vital international criminal databases, which document crimes like those of Zalkalns, could allow other violent and sexual offenders to slip through the net.

Facebook Twitter Pinterest Nina Gross, whose sister was killed in 2014, with her artworks. Photograph: Linda Nylind/The Guardian

“We are talking about a very small number of people who have committed violent and sexual offences,” Gross says. “If we leave the EU without a deal people will be put at risk. We need some sort of guarantee that we will continue to be part of the system we’re part of at the moment. We need a proactive rather than a reactive system.”

The databases the UK currently has access to include ECRIS – the European Criminal Record Information System – and Europol allows UK police and immigration officials access to information about violent killers and sex offenders, and vice versa. If the UK leaves the EU without a deal, access will end. But amid discussion of food shortages and medical hold-ups, the security implications of that fact have been lower on the agenda.

Gross fears that women and girls will be disproportionately affected if the monitoring system for this small but highly dangerous group of offenders is abandoned.

She and her family are at pains to emphasise that they support freedom of movement and are profoundly dismayed that Alice’s case has been exploited for what they view as xenophobic purposes.

Facebook Twitter Pinterest Alice Gross was murdered in 2014. Photograph: Metropolitan Police/PA

She and her parents, Jose Gross and Rosalind Hodgkiss, believe that Alice’s murder was hijacked by Johnson and Michael Gove who, in March 2016 as part of the Vote Leave campaign, published a dossier of 50 violent criminals who they claimed were able to come to the UK and commit crimes as a result of EU freedom of movement. Alice’s killer was one of them.

Despite the dossier’s implication that leaving the EU would prevent the threat of these violent individuals reaching our shores, Leave campaigners said nothing about how losing access to the EU criminal databases could actually increase rather than reduce the risk of violent individuals coming to the UK unchecked.

“Boris Johnson and Michael Gove were happy to use Alice’s case but they haven’t done anything about this issue,” says Gross. “I know that some people who voted to leave the EU will have been influenced by this list of 50 criminals. I want reassurances about how citizens will be protected if we fall out of ECRIS and Europol. The government has not been honest about this.”

Alice is thought to have been murdered in the late afternoon of 28 August 2014 while out for a walk. Her body was found 34 days later on the bed of the shallow river Brent in Hanwell, Ealing, having been intentionally weighted down and concealed.

Scotland Yard launched a huge search for her. Zalkalns killed himself shortly afterwards.

At the time of Alice’s murder, the effectiveness of the system for checking convictions of foreign nationals was, according to the presiding coroner Dr Fiona Wilcox, “limited by inconsistent levels of cooperation from such authorities and their policies on retention of criminal data”.

Facebook Twitter Pinterest Nina Gross’s artwork. Photograph: Linda Nylind/The Guardian

The coroner made recommendations, and levels of EU-wide cooperation and data-sharing have improved. Amber Rudd, then home secretary, provided a five-page response in September 2016. She stated: “Whilst it would be wrong to set out unilateral positions in advance of negotiations on options for future cooperation arrangements once the UK has left the EU, we will do what is necessary to keep people safe to ensure we have robust criminal records sharing arrangements in place when we leave the EU.”

Alice Gross's mother blames government for failures over daughter's killer Read more

Three years after that letter was written there is still no clarity about what those arrangements will be. “I don’t want another coroner to have to rule in the way a coroner did following Alice’s death,” Gross says.

Alice was a gifted musician and the family have set up a memorial fund for young musicians. Gross is working on a series of artworks using media reports and Facebook posts of the 34 days when her sister was missing, marking each of those days.

“Alice’s murder has had a devastating effect on our family,” she says. “It was a waste of a really good life. When you read about stories like this one you never think you are going to be in the middle of it. We were assured that nothing like this could happen again but unless systems are put in place citizens will not be protected. At the moment there is just a vacuum.”

A Home Office spokesperson said: “The murder of Alice Gross was a shocking and despicable crime. The continued safety and security of our citizens remains the top priority and we are committed to a close and ambitious security relationship with the EU which is in everyone’s interest.

“However, we continue to work closely with operational partners and engage with EU member states to ensure we are ready for a no-deal scenario and that data, such as criminal records, can continue to be exchanged. We will also be introducing tougher UK criminality thresholds both at the border and for deportation where we identify criminals in the UK.”