> The majority of overdose deaths in Scotland involved multiple drugs; for reasons that are not entirely clear, Scottish addicts are particularly prone to concurrently use opiates, benzodiazepines and alcohol in an indiscriminate manner.

I don't believe this is specific to Scotland. My layperson understanding is that heroin is relatively safe in the sense that most opioid deaths fall into one of the following categories: multiple drug interaction (benzos/alcohol being a very common combination), tolerance change due to relapse and, more recently, increased variance in potency due to strong synthetics (fentynyl, carfentanil, etc.). This is the theory behind people who advocate for maintenance prescriptions.