No. It's not certain at all. The facts are the facts. And the facts indicate that Portugal's homicide rate was 1.0 per 100,000 in 2001 when drugs were decriminalized. That rate rose. But by 2009 it was at 0.9. And as of 2018 it is at .08.
Portugal Homicide rate, 1990-2019 - knoema.com
Further, as the writer states, the 8 year increase in homicide was not determined to be drug-related homicides. And petty crimes increases were not of crimes associated with drug use.
Looking at Spain, which is right next door and has a similar demographic and government, but which does not have as comprehensive a decriminalization program as Portugal, the homicide rate was 1.4 in 2001 and is now down to about 0.7.
Spain Murder/Homicide Rate 1990-2020.
From your article:
-Drug use has declined among those aged 15-24,6 the population most at risk of initiating drug use
-Between 2000 and 2005 (the most recent years for which data are available) rates of problematic drug use and injecting drug use decreased
-Rates of continuation of drug use (i.e. the proportion of the population that have ever used an illicit drug and continue to do so) have decreased
- Deaths due to drug use have decreased significantly – from approximately 80 in 2001, to 16 in 2012.
You can't have a increase in crime due to decriminalization if drug use has actually decreased. That's not logical.
In the meantime, continuing our War on Drugs harsh approach, our homicide rate in the US is 2.5.
Crime in the United States - Wikipedia.
And our drug-induced death rate is five times higher than Portugal's.
Want to Win the War on Drugs? Portugal Might Have the Answer