Singapore’s death penalty for drug trafficking: What the research says and doesn’t

Academic Views / Saturday, October 7th, 2023

MAI SATO (Monash University) reviews studies conducted or commissioned by Singapore’s Ministry of Home Affairs that claim public backing for and the effectiveness of the death penalty in managing drug trafficking. Sato finds that these studies provide far weaker evidence for using the death penalty for drug trafficking than their authors and officials citing them claim. 

Editors’ note: Given the gravity of crimes like drug trafficking as well as of the taking of human life by the state, the death penalty for such offences is contentious. We think discussions about these issues should be based on evidence rather than ideology — regardless of the stance someone ultimately adopts. This article is a contribution to that process. We hope that Singapore can have more serious, empirically-informed conversations in good faith about maintaining and improving law and order in ways that are not only just, effective, and appropriate, but also proportionate and non-excessive. Like all policy tools, capital punishment is only a means to an end and not an end in itself.

Of all retentionist countries, Singapore seems to be the most vocal about the need  to execute individuals as a form of criminal punishment. The two top executing States — China and Iran — do so in silence, rarely responding to international criticism, but Singapore is keen to engage in discussion about the benefits of the death penalty. It often takes the lead in various United Nations fora in defending the use of the death penalty. It vigorously rebuts criticisms made by individuals, ranging from articles written by journalists and activists, such as Kirsten Han, to comments made by the founder of the Virgin Group, Richard Branson

National media such as The Straits Times appear to merely echo the administration’s narrative on why Singapore needs the death penalty for drug trafficking. Last month, it published an article entitled “Capital punishment for drug trafficking essential to saving more lives: Shanmugam”, which essentially summarised a speech that Law and Home Affairs Minister K. Shanmugam gave to youth leaders. Shanmugam quoted Ministry of Home Affairs (MHA) studies to back up the administration’s support for the death penalty. In this piece, I explore these claims by examining findings from the research conducted or commissioned by MHA. I am of the view that the available evidence does not provide as strong support for the use of the death penalty for drug trafficking as claimed. 

For this analysis, I wrote to MHA, requesting access to the studies. I was delighted to receive a response containing links to studies MHA completed. Disappointingly, the Ministry declined to share the anonymised raw data analysed in these studies, ruling out the possibility of secondary analysis and replication studies. The studies that have been made public were all carried out by Ministry staff, with one exception — a study commissioned by the Ministry and carried out by the Institute of Policy Studies (referred to as Study 3 below). 

The studies I analysed are the following:

In sum, these studies conclude that: (A) there is strong public support for the death penalty; and (B) the death penalty works as a deterrent in relation to capital offences. I analyse each of these conclusions in turn. For reasons of length, detailed comments on the studies are placed in the Appendix to this article.

A. ‘Overwhelming’ support for current policies 

According to The Straits Times article, Shanmugam said that the “overwhelming majority of people in Singapore today support the current drug policies”. In particular, he quoted “a survey which showed that 66 per cent of Singaporeans polled said the mandatory death penalty is appropriate for drug trafficking”.

The survey that Shanmugam referred to appears to be from Study 1. In this survey, MHA measured support for the use of the mandatory death penalty by asking respondents to what extent they agreed or disagreed with the following statement: “The mandatory death penalty is appropriate as the punishment for…trafficking a significant amount of drugs” (emphasis added). Based on this question, the Ministry concluded that 66% of respondents “strongly agree[d]” or “agree[d]” with the statement. Although not referred to by Shanmugam in this article, Study 2 also asked a similar question (see my Appendix). 

This question in Study 1 contains a qualifier: it asks support for the mandatory death penalty for “trafficking a significant amount of [illicit] drugs”. The survey does not examine what respondents consider a “significant amount” of drugs or whether their perceptions align with the law. Under the Misuse of Drugs Act 1973, trafficking the following amounts of illicit drugs carries the mandatory death penalty: 30g of morphine, 15g of diamorphine (pure heroin), 500g of cannabis, 200g of cannabis resin, 1,000g of cannabis mixture, 30g of cocaine, and 250g of methamphetamine. 

The above amounts are larger than those for possession offences; however, whether they are “large” in the context of trafficking may vary. For example, in the State of Victoria, Australia, where I reside, the quantity threshold for trafficking cocaine is 250g, and a “large” commercial quantity threshold is 750g (for other illicit drugs, see page 8 of this report by the Victorian Sentencing Advisory Council). 

This question uses a 5-point Likert scale question, ranging from “strongly agree”, “agree” and “neutral” to “disagree” and “strongly disagree”. A Likert scale allows us to understand different intensities of views, measuring how strongly (or not so strongly) one feels about a position. The authors of Study 1 chose to combine the respondents who selected “strongly agree” and “agree” when reporting the results, meaning it is not possible to determine the proportion of respondents who “strongly agree[d]” with using the mandatory death penalty for individuals who traffic this significant amount of illicit drugs.

Fortunately, Study 3 (not cited by Shanmugam in the article) provides insight into the proportion of respondents who strongly hold such views. They were asked to state the extent to which they agreed with the statement: “I believe the death penalty should be mandatory for a person convicted of intentionally trafficking a substantial amount of drugs”. This question narrows support for the mandatory death penalty to individuals who have trafficked a substantial amount of illicit drugs with intention, which excludes those who did not know that they were carrying illicit drugs (but probably includes those who were coerced into doing so). Combining respondents who selected “strongly agree” or “agree” with this statement, one could conclude that 62% are in support of such policy, yielding similar results to Study 1 quoted by the minister. However, respondents who “strongly” supported this view in Study 3 only amounted to 19%. Again, though, it is not possible to know what respondents in Study 3 had in mind with regard to “a substantial amount” of illicit drugs as it is not included with the question.

In sum, I would summarise the level of support for the death penalty for drug offences in this manner, based on studies examined so far: around 62-66% of the Singaporean public “strongly agree” or “agree” with the use of the mandatory death penalty for individuals who traffic illicit drugs in significant/substantial quantities, though it is unclear what respondents mean by this. Those who strongly support this view are a minority (based on findings from Study 3). Another qualifier I would add when interpreting these studies is the respondents’ level of knowledge on the death penalty, to which I now turn.  

How knowledgeable is the public? 

If public support for the death penalty justifies Singapore’s use of this ultimate punishment, ideally such support should be informed by at least a basic understanding concerning the policy. Study 3 investigated exactly that. It concluded that “[r]espondents were relatively knowledgeable about issues relating to the death penalty” (emphasis added). Based on the number of true-or-false questions respondents answered correctly out of 8, the study found that 11% had “low” knowledge (0-2 correct answers), 46% had “medium” knowledge (3-5 correct), and 44% “high” knowledge (6-8 correct). The statements presented to respondents ranged from “Singapore has the death penalty for intentional murder“, which 82% of respondents correctly identified as “true” to “In the last five years, fewer than five people were executed yearly in Singapore”, which 13% correctly decided was “false”. 

The veracity of 2 of the 8 statements, however, is worth further examination. One of the statements identified as “true” reads: “Singapore has the death penalty for drug traffickers who traffic a substantial amount of drugs (e.g., 1,250 straws of heroin, which can feed about 180 abusers for a week).” Leaving aside the use of the word “abuser” for people who use drugs, the Misuse of Drugs Act 1973 makes no reference to a “substantial” amount of drugs as a threshold for drug trafficking. Nor does the law refer to 1,250 straws of heroin; instead, it refers to 15g of diamorphine. In addition, given heroin is usually mixed with other substances, its strength is often unclear to the user and the preferred amount to be consumed also varies. 

Another question reads: “The death penalty is not imposed on persons who are suffering from certain mental illnesses.” To my knowledge, there is no law in Singapore with such a provision. For individuals accused of drug trafficking, however, amendments to the Misuse of Drugs Act state that judges have discretion to impose a life sentence instead of the death penalty, among other conditions, if the defendant’s “abnormality of mind…impaired his mental responsibility for his acts and omissions in relation to the offence”. 

However, in April 2022, Nagaenthran Dharmalingam was executed for trafficking some 43 grams of diamorphine. The court found that Dharmalingam, who had an IQ of 69 and attention hyperactivity disorder, was not suffering from intellectual disability but had borderline intellectual functioning. Accordingly, it is worth questioning whether agreement with these two statements is a suitable indicator of respondents’ knowledge of the death penalty. 

The study does not report the correlation between respondents’ level of knowledge and their attitudes towards the death penalty for drug trafficking. The study could have run a regression analysis to see whether the more knowledgeable respondents are, the more “strongly” they agreed with the statement that “the death penalty should be mandatory for a person convicted of intentionally trafficking a substantial amount of [illicit] drugs”. If, on the contrary, respondents in strong agreement had low knowledge of the facts, one would need to question the wisdom of basing policy on their opinions.

What to make of these attitudinal studies?

The fact that the Government of Singapore has carried out or commissioned these studies is evidence that it cares about what people think about the death penalty. As a parliamentary democracy, Singapore treats public support for official policy as important as a matter of principle. Hence, I have no issue with the government of Singapore conducting these attitudinal studies on the death penalty. 

However, a severe punishment that intentionally takes away life must be properly justified. In my opinion, it is not enough that the public prefers to retain the death penalty. While surveys may show public preference for the death penalty, the public may still accept abolition as legitimate. Existing research suggests that public preferences and their aggregation can be complex. Leaving aside other issues discussed above, studies 1-3 examined here clearly show public preference for the death penalty for drug trafficking offences — but the results do not portray a public that is clamouring for drug traffickers to be executed.

For a retentionist country like Singapore, surveys of this nature should also try to understand how important the death penalty is to the public, and measure possible adverse reactions to abolition. The survey should ask retentionists why the death penalty is important to them, and examine possible consequences that could follow from abolition. These might include, for example, erosion of public perceptions of the legitimacy of the criminal justice system, resulting in non-compliance with the law, lack of cooperation with the criminal justice system, and even vigilantism. 

It is conceivable that retention is central to public trust in the criminal justice system, and that abolition would therefore result in the erosion of political and judicial legitimacy. In such a scenario,  moving away from the death penalty could prove dangerous to a state. However, evidence from countries that retain the death penalty has shown that the legitimacy of the justice system does not always hinge on retention of the death penalty., Instead, public attitudes show enough flexibility to embrace abolition (see examples from Japan; Zimbabwe; China; Malaysia). 

Indeed, an academic study carried out in Singapore in 2016 came to a similar conclusion: 

There is unlikely to be any adverse outcry should the Government further relax the criteria for life imprisonment to be granted for these offences or review other offences carrying the death penalty. There is in fact no strong interest or active discussion on the topic. Increasing the number of executions is generally not thought to be an effective measure to reduce violent crime or drug trafficking …The overall findings of this survey show that while a majority of the public is in favour of the death penalty when the question is asked in general terms, it is certainly not an opinion which is held strongly or unconditionally.

Perceptions about deterrent effects 

Returning to Shanmugam’s speech, he was reported as justifying the need for the death penalty with the following argument: “Another Ministry of Home Affairs (MHA) survey — which was conducted among people from places where most of the drug traffickers arrested in Singapore in recent years had originated from — showed that 87 per cent of respondents believed capital punishment deterred people from trafficking large amounts of drugs into Singapore.” [Emphasis added.]

Shanmugam is likely to be referring to Study 4, which examined the perceived deterrent effect of the death penalty among individuals living in six unnamed regional cities However, Study 4 states that the cities were selected based on ‘the number of travellers from these cities who visited Singapore in recent years’ rather than based on the top six cities where individuals arrested for drug trafficking came from.  Unlike the studies examined above, the sample in Study 4 is not representative of the target population, meaning that the findings cannot be generalised beyond the sample.  

That being said, Study 4 showed that those living outside of Singapore did believe in the deterrent effect of the death penalty. The 87% figure quoted above comes from a question asking respondents the extent to which they agreed with the following statement: “I believe that the death penalty makes people not want to traffic substantial amounts of drugs into Singapore because of the potential of being caught, convicted, and sentenced to death.” The 87% figure is the average value of respondents from 6 cities who “strongly agreed” or “agreed” with the statement. 

Leaving aside the issues concerning the sample, Study 4 shows that in six (unspecified) cities outside of Singapore, the majority of respondents believed in the deterrent effect of the death penalty. Politically, this finding may suffice to justify the retention of the death penalty to the Singaporean public. However, scientifically speaking, deterrence is an empirical matter that does not depend on whether the people inside or outside of Singapore believe in it. It is not a matter of opinion.

B. Deterrence-based model of crime control

Shanmugam defended the mandatory death penalty for drug trafficking by stating that “the drug laws would be unworkable otherwise”. The Straits Times reported his justification thus: “It was necessary to be clear about the consequences in order for these laws to effectively act as a deterrent. ‘Once there are question marks around it, then more people (will) take a chance.’”

Theoretically speaking, if the deterrence model were to work, would-be offenders would have to go through a certain decision-making process.

First, he or she must have knowledge of the punishment assigned to the offence

Second, the would-be-offender must have some sense of the certainty of punishment; the offender needs to predict: 1) the likelihood of being caught by the police; 2) the likelihood of being charged, convicted and sentenced to death; 3) the likelihood of the death sentence being confirmed on appeal; followed by 4) the likelihood of execution. Accordingly, the mandatory death penalty is relevant only to the sentencing part of the model. 

Third, in addition to knowledge of the law and calculation of the odds of being executed, the would-be-offender needs to act rationally, balancing the costs and benefits of offending. However, offender rationality will not apply in situations where the offender acts in a moment of anger, fear or other situations when rational thinking has been suspended. Similarly, some offenders may commit a capital offence under coercion or if they are duped. Study 5 attempted to examine the decision-making process of individuals who traffic illicit drugs. Interestingly, the study also showed that there are plenty of convicted drug traffickers who did not think rationally following the decision-making model outlined above. (See quotes on page 70 of the study. Also see my Appendix for a more detailed analysis of the study).

Proving the deterrent effect

Study 6 contained a review of literature on the deterrent effect of the death penalty. The review is correct in that studies on this topic are predominantly US-based investigations focused on whether the death penalty deters homicides. However, the review in Study 6 seems misleading in that it fails to make clear that it is impossible to prove the extent to which the death penalty is an effective deterrent relative to other punishments. This is because all deterrence studies are observational; it would be impossible to carry out an experiment to test the crime rate of a country with and without the death penalty, with all other conditions being equal. This point is relevant to any jurisdiction, including Singapore, as a National Academies of Sciences review points out. (Study 6 also refers to this review.) 

In other words, one may cite an increase or decrease in crime rates or convictions as (dis)proof of the deterrent effect of the death penalty, comparing two time points, or two regions, with and without the death penalty. However, these statistics do not prove the (lack of) deterrent effect of capital punishment. They may suggest that the two variables — the number of executions (or any other intervention) and crime rates — may be correlated but this does not prove causation. Other factors, unrelated to the existence or the lack of death penalty, could have caused the fluctuation in crime rates, not the number of executions. In addition, these figures do not demonstrate the relative impact of capital punishment, compared to other punishments, such as prison sentences. Based on the understanding that it is impossible to provide clinching evidence on this matter, the National Academies of Sciences’ reviewed existing US studies undertaken since 1978 on tentative evidence concerning deterrent effect of the death penalty and reached the following conclusion:

The committee concludes that research to date on the effect of capital punishment on homicide is not informative about whether capital punishment decreases, increases, or has no effect on homicide rates. Therefore, the committee recommends that these studies not be used to inform deliberations requiring judgments about the effect of the death penalty on homicide. Consequently, claims that research demonstrates that capital punishment decreases or increases the homicide rate by a specified amount or has no effect on the homicide rate should not influence policy judgments about capital punishment.

Study 6 used data from the Central Narcotics Bureau to examine whether amendments to the Misuse of Drugs Act introduced in 1990 for cannabis and opium had the effect of deterring trafficking in these illicit drugs. This observational study concluded that the changes in law “likely” had a deterrent effect — with which I disagree based on the methodology used and the conclusions drawn from the analysis, taking into consideration various assumptions and limitations of the study design (see the Appendix for my detailed analysis of this study). 

Concluding remarks

In this piece, I have focused on the death penalty for drugs, given that Singapore’s recent executions have all been for drug offences. 

International standards restrict the application of the death penalty to intentional murder, and less than half of countries that retain the death penalty in law or in practice execute for drug offences. The United Nations Office for Drugs and Crime — the very agency responsible for enforcing global prohibition of illicit drugs — acknowledged in 2015 that international drug policy based on criminal punishment has created a “lucrative and violent black market”. It is widely accepted among drug policy experts that the global war on illicit drugs has failed, with devastating consequences for individuals and societies around the world. 

Instead of disrupting drug cartels, capital drug laws in practice often operate to punish those who are typically recruited from marginalised groups with intersecting vulnerabilities, and who are easily replaced if arrested. There are other perverse consequences of vigorous enforcement action against drug distribution. Crackdowns on drug markets inevitably drive out risk-averse dealers and draw in replacements with larger tolerance of risk and greater appetites for violence. And those crackdowns that are successful in reducing the availability of illicit drugs may simply drive up prices, given the inelasticity of demand for illicit drugs, especially when they are addictive. In this sense, States that impose the death penalty for drug offenses are in fact part of the illicit drug market.

Shanmugam made it clear that “the death penalty is not something that any government would start off wanting to have”, and that the government must be sure that it is “essential to saving more lives”. The key message from his speech is that the government does not want to use the death penalty for drug trafficking but is reluctantly doing so based on the consequentialist position that having it “saves more lives” than not having it. The studies examined in this piece do not oblige the government to retain the death penalty. Based on MHA’s research, current evidence on the deterrent effect of the death penalty for drug trafficking is too weak to demonstrate effectiveness. In addition, the Singaporean public does not appear to be clamouring for the retention of the death penalty for drug trafficking. Whom and what purpose the death penalty serves in Singapore remains unanswered.

Mai is the inaugural director of Eleos Justice at Monash University. She is the author of The Death Penalty in Japan: Will the Public Tolerate Abolition? (Springer, 2014). Mai also created and co-runs an NGO, CrimeInfo, which promotes the abolition of the death penalty in Japan. Mai has a PhD from King’s College London. She has also worked at the Australian National University, University of Reading, University of Oxford, and at the Institute for Criminal Policy Research (UK).