"There is a proposal in the UK to implant "machine-readable" microchips under the skin of thousands of offenders in an effort to free up more space in British jails. The article states that uses are being considered both for home detention, as a means to enforce punishment, as well as for sex offenders after their release. Many view this as a slippery slope leading to much wider use; starting as a purely voluntary act and gradually becoming more compulsory, it would endanger human rights and privacy. There are also health questions involved, given that long-term studies have linked similar implants to cancer in lab mice and rats. Ironically, the same technology has been proposed for medical purposes as well. In the USA, some state agencies have already made decisions about this issue.