By Jon Silverman
Legal affairs analyst
The use of tagging raises a lot of important issues for criminal justice.
Does it represent value for money? Does it provide a safety valve for a prison service struggling to cope with rising numbers? Does it offer a measure of public protection? Does it have an impact on re-offending? Let's take them in turn.
Tagging is cheaper than prison
Compared with custody, electronic monitoring is cheaper. In February 2006, the National Audit Office found that it cost £1,300 to monitor an offender on "home detention curfew" (HDC) for 90 days. For the same period in custody, the bill was £6,500.
But in 2004/5, the Home Office spent £102m on electronic monitoring of curfews. Even allowing for a fall in the cost of the most recent contracts awarded to the private sector, does this represent value for money?
"The key question," said Dick Whitfield, former chief probation officer of Kent and an expert on tagging, "is: could the money be better spent? The answer is yes - on community punishments.
"But where the choice is between tagging and prison, then it does clear out the cells and eases the pressure on the prison service."
Deciding who should be released on HDC is a matter of risk assessment. Those convicted of serious violent crimes and sex offences are not eligible.
Of those who are, there is no evidence that prison governors are being reckless in approving early release under monitoring.
Indeed, the National Audit Office found that only 59% of prisoners assessed as suitable for HDC were released as soon as they were eligible, because governors were waiting for reports from probation, other prisons or from the police.
Dick Whitfield said a risk assessment in prison was always going to have severe limitations.
"It is what we call 'static', in other words, it is based on an offender's past or perhaps their behaviour in prison.
"An assessment made in the community is 'dynamic' because it can take into account what is happening to an offender here and now."
It is also a serious omission that governors get no feedback on what happens to people released on HDC.
For the chief executive of the Probation Boards Association, Martin Wargent, the report on re-offending raises worrying questions about the performance of the private companies monitoring releases on HDC.
"It is alarming that half of those who breached were not returned to prison for eight days, and a quarter for longer than that.
"A tag can't find someone a job or give them a secure home life. It can only ever be a limited safeguard."
As far as re-offending is concerned, Home Office claims that under 4% of those released on HDC since 1999 have committed further crimes do not tally with other criminal justice figures.
Home Office research in 2001 suggested that HDC was "broadly neutral" in its impact on re-offending and it is accepted that more work needs to be done to establish whether it has a rehabilitative function as well as preventing the prison service from buckling under the sheer weight of numbers.