38. As part of an international treaty, the term “most serious crimes” should be understood as an international standard applicable to all States. States cannot claim compliance with article 6 (2) merely because the crime is seen as serious in their specific context. …Inasmuch as an international standard is meant to reflect international consensus, it is noteworthy that several States are questioning the appropriateness of using the criminal law model for drug control. (…)
47. …As measured by State practice, however, there is no consensus among States to support the death penalty for crimes that do not involve lethal intent and that do not result in death, such as drug-related offences or economic crimes. In reality, many of these death-eligible crimes are not prosecuted by retentionist States as capital offences and/or death sentences are not handed down for them. Even fewer States actually carry out executions for these offences.
The UN Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions is appointed by the UN Human Rights Council.
This office, like the Human Rights Committee, the Secretary General, and other UN human rights mechanisms has found that drug offences do not meet the threshold of most serious crimes.
Referenced here is the Special Rapporteur’s 2012 report to the General Assembly in which the current Special Rapporteur, Chrsitof Heyns, challenges States that claim that ‘most serious crimes’ is a context specific issue (ie for each state to determine) and challenges arguments relating to consensus.