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Opiates and Heroin


Heroin is one of the most commonly abused illicit drugs in Singapore and its users are exposed to a considerable risk of physical harm when they administer the substance via intravenous injection or when accidentally overdosing. Traffickers in heroin also face among the harshest criminal penalties in the world, with a mandatory death penalty in place for convicted of trafficking more than 15g of the substance.

The following article is divided into 4 parts. Part I is dedicated to a basic understanding of what heroin is and how it operates on the human body. Part II offers a brief look into the potential harms of heroin use while Part III provides an overview of the forensic testing for heroin use and the legal provisions that enable such methods. Part IV departs from its preceding sections by delving a little deeper into the international law on opiate control and an Asian perspective on the future of opiate controls.

Part I: Background and Scientific Facts

What is heroin?

Heroin, also known as diamorphine or diacetylmorphine, belongs to the opiate class of drugs and has an analgesic effect on users. It is synthesized from morphine, which is itself naturally occurring and can be extracted from the sap of poppy (opium) plants. Much of the world’s opium supply originates from Afghanistan.

How do users consume/administer heroin?

The most common routes of administration for heroin are through inhalation after heating (“chasing the dragon”) or through direct intravenous injection into the blood stream. It is seldom ingested by users.

How does heroin operate on the body?

Heroin operates on the body by inhibiting the central nervous system and thereby dulling the user’s senses – in particular, pain – and causing a relaxing sensation, which is called an analgesic effect. This puts users into a state of calmness and euphoria very quickly after the initial administration of the drug. The rapid euphoric effect is induced mere minutes post-administration and is called a “rush”, which is a sensation many users seek to achieve. A common historical anecdote of Singapore’s past is the use of opium by Chinese coolies (labourers) to alleviate the physical pain of their back-breaking labour.

Heroin first enters the bloodstream through the aforesaid routes of administration. When intravenously injected, heroin enters the bloodstream directly and when inhaled, it enters the bloodstream by passing through the alveoli cells of the lungs and into the surrounding blood capillaries.

In human blood, heroin is broken down and metabolised within minutes into morphine and other metabolites such as 3-monoacetylmorphine and 6-monoacetylmorphine due to the chemical and biological properties of blood plasma and tissue. These properties include the pH of the plasma and the presence of enzymes which metabolise diamorphine. Consequently, heroin in its original form becomes undetectable in blood less than one hour after administration, and this has implications on what methods must be employed to effectively test for the consumption of heroin. 

Morphine is one of the metabolites of heroin and is thought to be primarily responsible for the analgesic effects experienced by heroin users. When the morphine reaches the central nervous system and brain, it binds to and inhibits μ-opioid receptors (pronounced “mu-opioid receptor”) found throughout this organ system, thus disrupting the transmission of pain signals throughout the body. This is the ultimate effect desired by heroin users, where their senses of pain are dulled, and a state of relaxation is induced by heroin’s effect on the nervous system.

Part II: The Addiction Potential and Harms of Heroin

It is relatively common knowledge that heroin is a highly addictive substance, along with many of the other illicit drugs found in Singapore. There are two types of dependencies that heroin use can induce – physical and psychological dependence.

Psychological dependence on a drug occurs when a user turns to the substance to alleviate emotional needs and to promote a sense of wellbeing and relief. Physical dependence, on the other hand, is characterised by the onset of withdrawal symptoms that may cause considerable pain and discomfort if the administration of the substance is suddenly stopped.

In the case of heroin users, withdrawal symptoms can be intensely uncomfortable and last for several days. Such symptoms may include dysphoria, insomnia, muscle aches, nausea, fever, sweating, vomiting, and diarrhoea and in some rare cases, heroin withdrawal can be life-threatening.

There has not been a large amount of research engaging in a comparative analysis on the potential for harm (in a broad sense of the word) across various drugs. In other words, few studies can tell us how harmful heroin is compared to other substances of abuse and for that reason, the classification of drugs under the First Schedule of the Misuse of Drugs Act (the “MDA”) into Class A, B and C controlled drugs may rightly be criticised for not being based on rigorous scientific evidence. 

Notwithstanding the relative harmfulness of other illicit substances however, in at least one study that aimed to devise a science-based harms ranking, heroin was unequivocally considered to be the most harmful of the substances under consideration. Some contributory factors taken in this ranking include heroin’s high propensity to induce physical and psychological dependence as well as the physical harms suffered by users as a result of the intravenous administration of the drug. 

Part III: Heroin and the Law

Forensic drug testing for heroin

An earlier article from CJC-F has provided a brief overview of the forensic testing of hair, blood and urine samples for the presence of illicit drugs. 

As mentioned above, heroin is very quickly broken down into its metabolites once it enters human blood and generally cannot be detected in its original form. Therefore, in order to successfully make out a criminal charge against a suspect for the consumption of heroin, forensic toxicologists need to test for a metabolite that is specific to heroin. A well-established confirmatory test for the consumption of heroin is to test for 6-monoacetylmorphine, which is a unique metabolite resulting from heroin consumption and thus presents conclusive evidence that a suspect had consumed heroin. 

Such confirmatory tests are important because other detectable metabolites of heroin such as morphine are shared with other opiates such as morphine and codeine, which may be prescribed in medical settings or found in common medications. This would present a legal obstacle in framing a drug consumption charge.

Local courts have accepted the validity and conclusiveness of the 6-monoacetyl confirmatory test in a number of judicial decisions, although it should be noted that none of these cases saw fully substantiated challenges based on expert opinion against this scientific position.

Notably, in PP v Lemmont Tan Beehunt, the District Judge was willing to accept that “monoacetylmorphine was a unique metabolite of diamorphine,” and convicted the accused of drug consumption charges. On appeal, the conviction was overturned by the High Court when Mr. Tan – who was unrepresented – successfully raised a reasonable doubt that traditional Chinese medicine peddled by a street vendor could contain trace amounts of illegal drugs. His case was supported in part by the improper seizure of evidence by the CNB officers.

Although the 6-monoacetylmorphine confirmatory urine test has been accepted by our courts, a significant limitation to its effectiveness is the fact that the detection window of 6-monoacetylmorphine in urine is usually smaller than 8 hours due to its short half-life of about 0.6 hours, beyond which instrumental analysis can no longer detect the substance. In other words, a urine sample would need to be obtained within 8 hours of the initial administration of heroin for the confirmatory test to work. In many cases this would be operationally or logistically impossible. 

As of 2013, law enforcement agencies have been statutorily empowered to require a person suspected of consuming a controlled drug to submit hair specimens for drug analysis. The toxicological analysis of hair in establishing prior consumption of heroin seems to offer a promising and reliable solution to the problem of low persistence of heroin and its metabolites in blood and urine.

One study examined hair samples from a group of 20 “heavy” heroin users and found that in each case, 6-monoacetylmorphine was detected in their hair. However, the same study also noted that there was a significant risk of environmental contamination of the hair samples that could potentially lead to a false positive result that is not attributable to an intentional administration of the drug.


Statutory powers of testing

Pursuant to Section 31 and 31A of the MDA, certain officers from the CNB, Singapore Police Force and immigration authorities may order the production of urine and hair specimens for testing if they suspect a person has consumed a controlled or specific drug under Section 8(b) of the MDA. More details on the offence of drug consumption can be found in a dedicated article by CJC-F. It is an offence not to comply with the order to provide a specimen without a reasonable excuse, pursuant to Sections 31(2) and 31A(2) of the MDA.

Part IV: International Opiate Control

The following Part far exceeds the familiar territory of forensic science and drug use. Nevertheless, the international efforts to regulate the supply of heroin and other opiates is worthy of special mention in this article because the 1912 International Opium Convention (the “Convention”) represents the first joint international effort to control drug use. The rich history on the origin of the Convention is relevant to developing a fuller appreciation of the divergence in global attitudes towards the continued regulation of opiates and other drugs.

A good starting point for analysis is the First Opium War. Fought between various Western powers and Imperial China from 1839-1842, it culminated in a humiliating Chinese defeat and the 1842 Treaty of Nanking (the “Treaty”). The war was essentially sparked by the Qing government’s confiscation of British opium imports which were officially considered contraband. 

Under the Treaty, China was forced to allow the victorious Western powers to continue to ply the opium trade and flood the Chinese markets with opium, which was detrimental to China’s society and its economic trade balance. Additionally, as a condition of the Treaty, Hong Kong was ceded to the British– it would not be an exaggeration to say that the First Opium War was what kickstarted the Chinese Century of Humiliation, and the aftershocks of these events continue to be felt generations later even in today’s political field. After the war, the growth of domestic consumption of opium in China accelerated, as did the domestic production of opium. 

The world had become a rather different place decades later, in the early 1900s. A large number of factors brought about a general shift in societal attitudes towards opium use amongst the influential global powers which collectively decided to adopt an anti-opium stance. 

For the Chinese, the opium trade had long been a source of humiliation and a symbol of Western dominance – thus, in 1906, the Qing Court reintroduced gradual curbs on the trade and use of opium. Meanwhile, European colonial powers in general had begun to take on a decidedly more beneficent policy stance in the administration of their colonies, realising a moral imperative to nurture their growth in a less exploitative manner. 

In particular, the British anti-imperialist movement was gaining widespread political influence domestically – partially due to the work of British missionaries and businessmen who formed the Anglo-Oriental Society for the Suppression of the Opium Trade. These groups campaigned for the abolition of the British opium trade in China after having travelled there and witnessing the opium situation first-hand, thereafter returning to Britain and condemning their government for employing such degrading colonial tactics. 

The Americans, for their part, were motivated by a desire to use joint international efforts to curb the uncontrollable inflow of opium from China into their newly acquired colony – the Philippines, which was causing social issues there.

Thus, in the early 1900s the stage was set for the major powers of the world to convene with an aim to promote a joint international effort to control the opium trade through international law. Given the centrality of China in the global opium trade, it is unsurprising that the process of drafting the 1912 Convention began with the International Commission convening in Shanghai in 1909.

The rest is history. The 1912 Convention entered into force on 28 June 1919 and, broadly speaking, it imposed on State Parties an international obligation to curb or prohibit the export of raw and “prepared opium” (products refined from raw opium, including heroin) to other State Parties to the Convention. The 1912 Convention was officially superseded by the 1961 Single Convention on Narcotic Drugs, which is more comprehensive and encompasses a wider variety of substances beyond opiates. With 186 State Parties, the 1961 Convention has attained near-universal acceptance in the world today – but that is perhaps a topic better left for another article.

This rather lengthy historical discourse is essential in appreciating how the general global anti-opium stance came to be. Only by understanding the troubled past of opium can we understand the divergence of views moving forward, where it seems that an increasing number of Western liberal democracies have been on the trajectory of decriminalising drug use whereas Asia in general maintains extremely strict anti-drug laws.

The genesis of the Western anti-opium sentiment stems from the colonial mindset of the White Man’s Burden and Judeo-Christian moral principles. These driving factors are perhaps less relevant today than they were over a century ago, with the end of the colonial age and the declining influence of Judeo-Christian morality on society and governance in general.

Conversely, the Eastern experience is deeply rooted in the shame of colonialization and the opium trade is inextricably linked to Western imperialism. The Chinese experience was not unique, and even in the Straits Settlements the opium trade generated nearly 50% of the colonial revenue, and it seems unlikely that these painful historical lessons will be easily forgotten.

Based on this historical narrative, it seems that the future of the global drug trade as whole will continue to diverge between the East and West for quite some time to come.


This article has given a brief overview of how heroin is typically administered and how it operates on the human body, generating a “high” sensation and analgesic effects by inhibiting the central nervous system. It then went on to explain the harms of heroin in terms of its addiction potential and the dependencies induced by its use. 

The article then went on to discuss the forensic methods used to test for the illegal consumption of heroin through the detection of 6-monoacetylmorphine, which is a unique metabolite of heroin. It went on to consider the challenges faced when employing existing methods – in particular, the very short half-life of the unique metabolite. It also considered the potential for forensic hair testing to provide a substantially larger detection window for heroin consumption.

The final part of the article presented a historical narrative on how international law arrived at its present anti-opium and anti-drugs stance. The narrative begins in mid-19th Century China and continues to unfold as the global West seems to be leaning in the direction of the decriminalisation or legalisation of drugs whereas the global East appears to be holding firm to its harsh anti-drug stance. This article then proffers an explanation for this divergence in attitudes – namely, the fact that the Eastern perspective is more deeply scarred by the humiliating effects of colonialization


1. Afghan Opium Production Jumps to Record Level, up 87 per Cent: Survey’, United Nations : Office on Drugs and Crime, accessed 10 March 2021, //www.unodc.org/unodc/en/press/releases/2017/November/afghan-opium-production-jumps-to-record-level–up-87-per-cent_-survey.html.

2. Elisabeth Rook et al., ‘Pharmacokinetics and Pharmacokinetic Variability of Heroin and Its Metabolites: Review of the Literature’, Current Clinical Pharmacology 1, no. 1 (2006): 111, https://doi.org/10.2174/157488406775268219.

3. Rook et al., 111; Amanda J. Jenkins et al., ‘Pharmacokinetics and Pharmacodynamics of Smoked Heroin*’, Journal of Analytical Toxicology 18 (October 1994): 325, https://doi.org/10.1093/jat/18.6.317.

4. Medicurio, Opioid Drugs, Part 1: Mechanism of Action, 2018, https://www.youtube.com/watch?v=s60KzN4GJdQ.

5. Shane Darke, Sarah Larney, and Michael Farrell, ‘Yes, People Can Die from Opiate Withdrawal: Editorial’, Addiction 112, no. 2 (February 2017): 199, https://doi.org/10.1111/add.13512

6. David Nutt et al., ‘Development of a Rational Scale to Assess the Harm of Drugs of Potential Misuse’, The Lancet 369 (24 March 2007): 1047; 1051, https://doi.org/10.1016/S0140-6736(07)60464-4.

7. Celine Cheow, Tay Bo Wen Thomson, and Muhammad Khairul Fikri, ‘Illicit Drugs in Blood, Urine, and Hair’, NUS Criminal Justice Club (blog), accessed 9 March 2021, https://nuscriminaljustice.com/illicit-drugs-in-blood-urine-and-hair/.

8. See: PP v Nandakishor s/o Raj Pat Ahir [2012] SGDC 490 at [14] and the appeal in Nandakishor s/o Raj Pat Ahir v PP [2014] SGHC 121, although the specific point on monoacetylmorphine was no longer contested on appeal; PP v Kalemuthu Nagarajah [2015] SGDC 283 at [18]; PP v Ng Kok Mun [2018] SGDC 49 at [17]; PP v Mohamed Fauzy Bin Razali [2015] SGDC 237 at [20]-[29]; PP v Law Soo Khoon [2013] SGDC 69 at [8] and [14]; PP v Mohamed Raffi S/O M M Ibrahim [2015] SGDC 24 at [17]-[18]; PP v Mohamad Rashid Bin Mohamad Kassim [2015] SGDC 304 at [6]

9. PP v Lemmont Tan Beehunt [2018] SGDC 262 at [12]

10. Selina Lum, ‘Man Acquitted of Taking Heroin after He Raised “reasonable Doubt” about CNB Officer’, The Straits Times, 24 March 2017, https://www.straitstimes.com/singapore/courts-crime/man-acquitted-of-taking-heroin-after-he-raised-reasonable-doubt-about-cnb.

11. E. J. Cone et al., ‘Forensic Drug Testing for Opiates: I. Detection of 6-Acetylmorphine in Urine as an Indicator of Recent Heroin Exposure; Drug and Assay Considerations and Detection Times’, Journal of Analytical Toxicology 15 (February 1991): 6–7, https://doi.org/10.1093/jat/15.1.1.

12. Misuse of Drugs Act (Cap 185, 2008 Rev Ed Sing), s 31A

13. B. A. Goldberger et al., ‘Testing Human Hair for Drugs of Abuse. III. Identification of Heroin and 6-Acetylmorphine as Indicators of Heroin Use’, Journal of Analytical Toxicology 15 (October 1991): 230, https://doi.org/10.1093/jat/15.5.226.

14. Mohamed Sarhan and Muhammad Khairul Fikri, ‘Singapore’s Misuse of Drugs Act – A Primer’, NUS Criminal Justice Club (blog), accessed 9 March 2021, https://nuscriminaljustice.com/singapore-misuse-of-drugs-act-a-primer/

15. See generally: Immanuel C. Y. Hsü, The Rise of Modern China, 6th ed (New York: Oxford University Press, 2000), chap. 8.

16. Helena Barop, ‘Building the «Opium Evil» Consensus – The International Opium Commission of Shanghai’, Journal of Modern European History 13, no. 1 (February 2015): 118, https://doi.org/10.17104/1611-8944_2015_1_115.

17. Barop, 119.

18. Francis Burton Harrison, ‘Prohibition as Superiority: Policing Opium in South-East Asia, 1898-1925’, 2021, 256.

19. Barop, ‘Building the «Opium Evil» Consensus – The International Opium Commission of Shanghai’, 122–23.

20. Hamilton Wright, ‘The International Opium Commission’, The American Journal of International Law 3, no. 3 (July 1909): 670.

21. Bertil A. Renborg, ‘International Control of Narcotics’, Law and Contemporary Problems 22, no. 1 (Winter 1957): 86

22. ‘CHAPTER VI NARCOTIC DRUGS AND PSYCHOTROPIC SUBSTANCES – 2. International Opium Convention’, United Nations Treaty Collection, accessed 11 March 2021, https://treaties.un.org/pages/ViewDetailsIV.aspx?src=TREATY&mtdsg_no=VI-2&chapter=6&Temp=mtdsg4&clang=_en.

23. See generally: ‘Germany – The International Opium Convention, Signed at The Hague, January 23, 1912, and Subsequent Relative Papers [1922] LNTSer 29; 8 LNTS 187’, World Legal Information Institute – League of Nations Treaty Series, chap. I and II, accessed 11 March 2021, http://www.worldlii.org/int/other/LNTSer/1922/29.html.

24. Hamilton Wright, ‘The International Opium Commission’, 662.


Mitchell Leon Siu Kin
 is a final year student from the NUS Faculty of Law and is also pursuing a minor in Forensic Science. He works with CJC-F’s “Drugs & Forensics” project and elsewhere within CJC, he is a case manager with The Recourse Initiative. An aspiring criminal defence lawyer and former policeman, Mitchell has a keen interest in the application of forensic science in Singapore’s courtrooms.

Muhammad Khairul Fikri is a Year 3 undergraduate from the Faculty of Arts and Social Sciences. Khai is one of the Project Managers of “Drugs & Forensics”. He is pursuing a Major in Geography and two Minors; Forensic Science and Geographical Information Systems. He is interested in the applications of technology, particularly geospatial technologies, in forensic science and crime scene investigations.