The head of the European Parliament is calling for an international investigation into the murder of a prominent Maltese journalist who had earned a fearsome reputation for alleging corruption at the highest levels.

Daphne Caruana Galizia died instantly when a powerful bomb beneath her car exploded just after she had driven away from her home. Car bombs were also used to murder a café owner in 2014 and a fisherman last year, both of whom were believed to be mixed up in smuggling fuel from Libya, where it is heavily subsidized and frequently stolen, to Malta or Sicily. Caruana Galizia was understood to be working on the fuel smuggling story when she was killed.

The journalist’s family has accused Maltese premier Joseph Muscat of being at least complicit in the killing and say that Caruana Galizia’s investigations demonstrate that Malta is riddled with corruption. Therefore, no fair and impartial enquiry into her murder can be expected.

Malta has a population of less than half a million. The striking Valetta is by far and away Europe’s smallest capital. Those with power and influence in the country know each other well, even if rivalries, particularly between some families, are deep seated. In such an intimate society, investigating an unusual crime such as a car bombing ought to be relatively straightforward. Yet no one has ever been brought to trial for the two previous such bombings. Caruana Galizia’s relatives thus say that the Maltese police and courts cannot be trusted to mount a fair investigation.

This is an extremely serious allegation. There are those in the country who have argued that Caruana Galizia was becoming paranoid, accusing prominent people and institutions of corruption, fraud, money laundering and links with international organized crime, not simply the Italian Mafia but Russian gangsters as well. The journalist undoubtedly basked in her reputation as a troublemaker. But if some of her sensational articles were wrong, she should have been challenged in the courts. That is the way that mendacious journalism can be exposed and indeed punished. At the time of her murder there were 42 different libel actions against her for her widely-read blog Running Commentary which she began nine years ago

But she had also been subject to almost daily threats - the family home was firebombed twice and her dog was killed and laid on the doorstep. The perpetrators of these crimes were never found.

In some respects Malta’s reputation is on the line here. The call by EU parliament head Antonio Tajani for an international investigation may be unnecessary. Premier Muscat has asked for help from the US Federal Bureau of Investigation and a Dutch police forensic team. Doubtless these will produce extensive evidence, which may through DNA or fingerprints even actually identify one of the killers. But in the end it will be the Maltese police and investigating magistrates who will have the job of running down the murderers and then finding out if they were acting on behalf of others. How well Malta handles this could have a significant impact on its relations with the rest of the EU. The government may, with some justice, dismiss calls for a purely international investigation into the crime itself. However, what it must fear is an international investigation into the way it investigates Caruana Galizia’s assassination.