What is chemical castration? How does it work as a method to combat sex crimes?

SINGAPORE – Chemical castrations may be considered in Singapore if there is evidence showing that they are effective in bringing down crime rates, said Home Affairs Minister K. Shanmugam in a written response to a parliamentary question on Sept 8, as cases of sexual assault here are on the rise.

Here’s what to know about the procedure that has been used as both punishment and a form of treatment.

What is chemical castration?

Chemical castration is a drugs-based method used to reduce sex hormones, namely androgens like testosterone, to suppress libido or sex drive.

It is a temporary form of castration, in contrast with the permanent form of surgical castration.

Other names used to refer to chemical castration include hormone therapy, or androgen suppression therapy.

How does it work?

Anti-androgen medications can be injected under the skin to block hormone production in the testicles, where about 95 per cent of androgens, including testosterone and dihydrotestosterone, are made, according to Stanford University’s school of medicine.

The injections, which can be applied at the abdomen or buttocks, are not a one-time treatment and must be repeated for the effect to continue, with normal hormone production generally returning after treatment ceases.

Another method involves implants placed under the skin of the arm, back or neck to continuously release the hormone-suppressing medication.

Anti-androgen pills can also be taken orally to block the body’s ability to absorb male hormones.

What is the science behind it?

Chemical castration involves taking medications called LHRH (luteinising hormone-releasing hormones) or GnRH (gonadotropin-releasing hormones) agonists.

By taking the agonists, the pituitary gland reduces production of the hormones which normally send signals to the testicles to produce androgens.

This leads to an effect similar to surgical castration.

Chemical castration is also used as a medical treatment for some prostate and breast cancers that feed on sex hormones, according to Johns Hopkins University’s researchers.

Which Asian countries use it as a legal punishment?

In 2011, South Korea became the first country in Asia to use chemical castration on convicted paedophiles, with the period for its use capped at 15 years. The law was later expanded to include sex offenders like attempted rapists and those whose sexual crimes lead to injury or the death of minors below the age of 19.

Indonesia followed in 2020, when then president Joko Widodo signed a regulation that perpetrators of sexual violence against children under the age of 18 will also face chemical castration for a period up to two years.

In Thailand, chemical castration is voluntary, with offenders consenting to receive the treatment after evaluations by a psychiatrist and internal medicine specialist. The law, which came into effect in 2023, allows sex offenders to get an early release from prison in exchange for a hormone-blocking injection to reduce sexual urges.

Where else in the world is chemical castration allowed?

In the United States, several states including California, Texas, Alabama and Florida implement chemical castration laws for repeat or severe sex offenders.

In Europe, countries like Britain, Denmark and Germany offer voluntary chemical castration programmes, whereas it is a mandatory sentence in other countries like Poland and Russia.

What are the arguments and evidence for and against chemical castration?

The short answer for the effectiveness of chemical castration cannot be determined, said Paul Cheong, senior law lecturer at the Singapore University of Social Sciences’ School of Law, writing in the Singapore Law Gazette.

He pointed to the lack of consensus of when it should be triggered, who should bear the costs of treatment and monitoring, and the possibility of sex offenders abusing other drugs to counter those used for chemical castration.

“The cacophony of voices screaming for chemical castration is muted by the deafening silence of medical and legal literature,” he said.

Others also point to the ethical concerns involved, with doctors in Indonesia refusing to implement chemical castration when the law was introduced, and human rights researchers in the country calling the procedure “inhumane” and a “degrading” form of punishment.

Advocates for chemical castration point to its reversible nature, and a greater drop in recidivism in voluntary programmes where the offender consents to drug treatment alongside other procedures such as therapy.

For instance, in England, hormone-suppressing drugs are taken along with other forms of psychiatric treatment that target other causes of sexual offending, such as a desire for power and control.

In South Korea, a study by the Korean Institute of Criminology and Justice involving offenders who received hormonal drug treatments showed an overall reduction of sex offence recidivism by 92 per cent.

But officials have pointed to the high costs required to keep up the treatment, citing the figure of an estimated 5 million won (S$4,720) per offender a year. The need for continued treatment was also highlighted by a study noting that offenders experienced an unexpected surge in testosterone levels, with intense sexual drive and fantasy, during the first two months after treatment cessation.