By Andy Tighe Home affairs correspondent, BBC News

Critics say open-ended sentences are "unfair"

It's almost a decade since a predatory paedophile called Sidney Cooke was released from jail.

The 71-year-old had been given two life sentences for a series of crimes that included the systematic rape and abuse of two brothers over several years.

There was so much public revulsion and anger when he was freed that at one stage he was forced to live in a suite of cells at a police station for his own safety.

Cooke was eventually rearrested for other offences, but his release provoked widespread condemnation.

A few years later, in response to cases like Cooke's, the government introduced its plans for indeterminate public protection sentences (IPPs).

These could be handed down to criminals convicted of violent or sexual crimes carrying a maximum penalty of ten years or more in jail.

Whilst there would be a minimum sentence - or "tariff" - they were essentially open-ended. Prisoners would have to convince the Parole Board they no longer presented a risk to the public before they could be released.

Clear message

This was the government - and in particular, the then home secretary David Blunkett - talking tough on crime.

Judges were given a list of more than 150 offences, including rape, malicious wounding and arson, which qualified for the new sentences.

The message was clear - criminals who still presented a danger to society should not expect to be released.

Many inmates found there was no provision for the kind of rehabilitation programmes they needed to complete in order to qualify for release

The judiciary listened, and acted. Over 3,800 public protection sentences were given in less than three years, often to defendants who were simultaneously given relatively short minimum tariffs.

Meanwhile, prison overcrowding was approaching crisis point. The Prison Governors' Association blamed the new indefinite sentences for putting extra strain on already-overstretched resources.

In particular, many inmates found there was no provision for the kind of rehabilitation programmes they needed to complete in order to qualify for release.

'Inadequate system'

Friday's Court of Appeal ruling accepts this was unlawful. But it stops short of saying that prisoners who have reached their "tariff" should be freed if the necessary courses are not available.

It does, however, warn ministers that holding inmates for long periods without a meaningful review of their status could be a breach of their human rights. A warning, in other words, that something needs to be done.

The Ministry of Justice, in response, says that measures are already in place that will alleviate the situation.

In particular, judges will be told not to pass indeterminate sentences for crimes attracting a minimum tariff of less than two years.

The Prison Reform Trust has called it the "beginning of the end of these unfair and unnecessary sentences".