The European Union’s highest court concluded that governments cannot hold phone data broadly and indiscriminately but that they can utilize specific information to combat the most severe crimes.

The court decided on a case presented by the Supreme Court of Ireland. A man convicted to life in prison for murder in 2015 filed an appeal, claiming that the court had accepted traffic and location data from phone conversations evidence unlawfully.

It is the national courts’ prerogative whether to use data or not

The European Court of Justice (ECJ) in Luxembourg states that it was up to a national court to determine whether the data may be used or not. However, it also stated that members of the bloc could not enact legislation that allows for deterring crime through the “general and indiscriminate” holding of such data.

Some instances, such as severe criminality that poses a national security concern, may warrant data retention, but only to a limited extent or for a short period of time.

The caveat that comes with leeway

Last year, the European Court of Justice (ECJ) decided that such data might be used to fight serious crime or be used as a deterrent against significant dangers to public security.

This issue hit the spotlight when the European Court of Justice ruled in favor of Graham Dwyer, who was convicted of murder in 2015, based on phone metadata, potentially impacting similar cases across the bloc. Dwyer was a successful architect who killed a childcare worker in august 2012 after he groomed her for sadomasochistic fantasies that involved stabbing women during sex.

Tip: EU-US data transfers will soon be legal, new Privacy Shield under way