Today marks one year since the brutal assassination of Daphne Caruana Galizia, Malta’s leading investigative journalist and anti-corruption campaigner. At 3pm on 16 October 2017, as she drove away from her family home, a bomb placed under her car was detonated. She was 53 years old. The last words she wrote were: “There are crooks everywhere, the situation is desperate.”

Twelve months on, justice for her murder remains elusive. The case has stalled and there are major concerns about the independence, impartiality and effectiveness of the Maltese authorities’ investigation. Despite her reporting on corruption at the highest levels of government, no politician has been questioned. Her family fears that those who ordered her death will never be brought to justice, that they will quite literally get away with murder.

Impunity for the killings of journalists drives a cycle of violence. Throughout her 30 years as a journalist, Caruana Galizia faced countless threats, suffering harassment online and off. Her house was set on fire; her family’s pet dogs were killed. She faced legal threats to stop her reporting, too: at the time of her death 43 libel cases were pending against her, many from high-level politicians.

She died without access to her bank account, which had been frozen thanks to one of those cases, lodged by Malta’s economy minister. Those behind the death threats Caruana Galizia received and the arson attacks on her home have never been identified and so remain unpunished. Some of the lawsuits against her remain (although not the one lodged by the economy minister), and are now being pursued against her husband and sons.

Since her assassination, a memorial that was erected as a protest for justice in her case has been repeatedly demolished by government workers. There are endless attacks on her reputation, as those who harassed her in life seek to erase her memory in death. Freedom of expression in Malta is deteriorating swiftly; the situation is indeed desperate.

When a journalist is murdered, all of society suffers. We lose our right to know, to speak, to learn.

Daphne Caruana Galizia had the courage and resilience to write despite the threats she faced. Today, on the anniversary of her assassination, the global membership of PEN International call again for justice in her case. To secure this, it is essential that there is a public inquiry to determine who commissioned her killing – and, crucially, whether it could have been prevented.

• Margaret Atwood is a novelist and a member of PEN International, a worldwide association of writers founded to promote friendship and intellectual cooperation between writers