A tamper-proof ankle tag that allows police and probation authorities to constantly monitor criminals’ alcohol consumption while they are on probation or bail is being introduced in states across the US.
Its developers have been approached by a firm interested in marketing the product to authorities in the UK, but said it could be some time before the system is made available here.
The Secure Continuous Remote Alcohol Monitor (SCRAM) Bracelet, developed by Denver firm Alcohol Monitoring Systems, weighs 227g and consists of two modules that are held on opposite sides of the subject’s ankle by a strap and a tamper clip, resembling an electronic ankle tag.
If a person is convicted of crimes such as drink driving or being drunk and disorderly, courts can use the system to impose a drinking ban as an alternative to prison.
The company has also had interest from airlines with a view to monitoring pilots’ alcohol consumption between flights. Last week three members of a British Airways crew were arrested in Oslo after allegedly failing a breath test, while earlier this year a BA captain was dismissed for an alleged alcohol-related offence.
SCRAM measures the ethanol content of insensible perspiration, the constant, unnoticeable excretion of sweat through the skin. The average person emits around one litre of this each day.
After drinking, alcohol is eliminated from the body by two mechanisms: metabolism and excretion. Over 90 per cent of ingested alcohol is metabolised by the liver, but the remaining 10 per cent is excreted unchanged through the breath, urine, perspiration and saliva. The amount of alcohol in these substances can be measured and correlated to determine a person’s blood alcohol content.
Following successful tests in Michigan and Los Angeles last year, states including California, Michigan, Minnesota, Texas and Indiana are now starting to use the device.
The unit consists of a sensor pack, which tests vapour as it migrates through the skin to determine alcohol concentration, and infrared electronics for tamper detection. It also contains systems for collecting, storing and transferring data to a modem via an RF link.
A tamper detection strap acts as an electronic link between the two parts and secures the bracelet to the ankle.
The wearer is unaware of when the SCRAM Bracelet is taking a reading, said Don White, vice-president of field operations.
‘A sample is taken from the ankle at a set time, such as every hour. Data is sent to a central server from the bracelet using a wireless link and can be accessed by authorised persons. People may try to fool it by covering their skin, but the system can detect this by measuring their temperature and taking a reading with the IR sensor. Not a lot of criminals know that substances such as plastic wrap and duct tape are gas permeable.’
Police or probation authorities can tailor the testing schedule around the individual requirements of the wearer. The data collected is date and time-stamped, and stored in a memory chip within the SCRAM Bracelet until it is transmitted for analysis.