Prosecutors in the murder case of Sion Grech have been forced to withdraw two of the lesser charges against two men charged with the 2005 crime because the offences were only introduced into the law months after she was killed.

Jurors hearing the case against Ismael Habesh and Faical Mahouanchi were told by prosecutor Anthony Vella that they should find the two men not guilty of having used a knife in a crime against the person and carrying a knife in public without a permit.

Speaking during closing arguments, Vella told the jury that the prosecution was withdrawing those two charges because those crimes were only introduced into local law through the Arms Act, which replaced the Arms Ordinance in August 2005, four months after Grech was murdered.

A key principle of law is that a person cannot be charged with a crime that was not a crime at the time when it was committed.

The prosecution’s error dents its case against Habesh and Mahouanchi but does not dismantle it, as jurors must still decide whether the two accused are guilty of the main charge, wilful homicide.

Prosecutors allege that Habesh and Mahouanchi assaulted Grech in a Marsa street, then dumped her in a field. Her decomposing body was found days later.

Over the course of the trial, jurors heard testimony indicating that Grech and Habesh were romantically involved, with the murder victim urging the accused to leave his wife for her.

They also heard that another woman, Jacqueline Rapinett, had told the police that she saw Habesh beat Grech and then, with the help of another man, carry her into a field.

Rapinett later led police to the exact spot where officers had discovered Grech’s dead body, the jury heard.

Jurors will in the coming days hear the defence’s reply to prosecutors’ closing arguments. They will then be addressed by Judge Aaron Bugeja, who is presiding over the court, before retiring to deliberate on a verdict concerning the two accused.

Lawyers Edward Gatt and Ishmael Psaila are representing Habesh. Mahouachi is represented by lawyer Simon Micallef Stafrace. Lawyer Roberto Montalto is appearing parte civile on behalf of the Grech family.