Talk:Geographical origin determination of cannabis

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Discussion for: Geographical origin determination of cannabis • View • Links • Related changes

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Page scope

Geographical origin determination of cannabis covers the measurement of cannabis material to work out where it was grown: stable isotope ratios of carbon, nitrogen, hydrogen, oxygen and strontium, infrared spectra read through statistical models, profiles of mineral elements, the reference material each comparison needs, the work done on seed, fibre and extracts, and what such a measurement can and cannot settle. Cannabinoid quantitation is treated at Potency testing, terpene profiles at Terpene profiling and the classification of plants by cannabinoid proportions at Chemotype.

Data verification

Record source conflicts, figures that differ between studies and the limits of what each study tested. Keep narrative content on the article.

Discussion

Sources

Denton and colleagues (2001), Australian Journal of Plant Physiology: carbon and nitrogen values of cannabis from Australia, Papua New Guinea and Thailand, the failure to separate the three countries, the values for watered and unwatered plants, for indoor and outdoor plants and for mineral and manure-based fertilisers, and the relation between soil, fertiliser and plant nitrogen.
West, Hurley and Ehleringer (2009), Journal of Forensic Sciences: 508 samples from known counties of the United States with further samples from one location, from Mexico and Colombia and from border seizures; inflorescences against leaves; the agreement with the supplying agency's record of indoor or outdoor growth.
West, Hurley, Dudás and Ehleringer (2009), Journal of Forensic Sciences: strontium ratios of cannabis grown in 79 counties against ratios modelled for the bedrock, and the pattern of anomalies.
Hurley, West and Ehleringer (2010), Science & Justice: models of region and growing environment from hydrogen and carbon values, tested against 60 specimens whose origins were withheld. Hurley, West and Ehleringer (2010), International Journal of Drug Policy: 628 retail seizures from more than 50 municipalities, grouped into 22 retail areas.
Booth and colleagues (2010), Forensic Science International: oxygen, hydrogen, carbon and nitrogen values of cannabis held in Alaska, for 56 samples from known sites in the state and for samples of unknown origin, and the very low carbon values attributed to carbon dioxide supplied in enclosed rooms.
Muccio and colleagues (2012), Journal of Forensic Sciences: bulk carbon values against values measured on the extracted cannabinoids for five samples, and the depletion of each cannabinoid relative to the bulk tissue.
Watling (1998), Journal of Analytical Atomic Spectrometry: patterns of association between elements, measured by laser ablation, applied to sourcing cannabis crops. Cited for its title and date.
Douvris and colleagues (2022), Toxics: twelve elements in cannabis seized in Ghana and in soils of cannabis farms there, and the association of the seized samples with two regions.
Rivi and colleagues (2025), Molecules: strontium ratios and elemental profiles of hemp stalks and fibre from several Italian regions, and the partial clustering of north and south.
Calvi and colleagues (2022), Separations: hydrogen, carbon, oxygen, sulphur and nitrogen values of roots, stems, inflorescences and seeds of hemp from eight Italian regions and of five seed oils.
Skoglund and Monti (2025), Fornvännen: strontium ratios of an Icelandic hemp fabric of the early 17th century against a soil sample and recently grown Icelandic hemp.
Perini and colleagues (2023), Antioxidants: hydrogen and oxygen values separating cannabidiol extracted from the plant from cannabidiol made by synthesis, with the thresholds given at a confidence level of 95 per cent.
Cucinotta and colleagues (2022), Analytical and Bioanalytical Chemistry: carbon values and the ratios of mirror-image forms of single terpenes in cannabis essential oils, and 19 oils bought in shops measured against the ranges of oils of known provenance.
Ramos and colleagues (2024), Forensic Sciences Research: infrared spectra of 47 Brazilian and 18 Colorado samples sorted by linear discriminant analysis, with the accuracies reported for each place.
Singh, Sharma and Sharma (2026), Spectrochimica Acta Part A: 200 flower tops from four regions of North India, 1,000 spectra, four models of which a neural network performed best, and the spectral component that contributed most. The paper carries a print issue date of February 2027 and was published online in September 2026.
Cerling and colleagues (2016), Annual Review of Earth and Planetary Sciences: the use of stable isotopes for comparing samples and for understanding the movement of goods, and the place of such evidence in legal proceedings.

Where the sources disagree

Whether isotope values separate countries. Denton and colleagues found that carbon and nitrogen values did not distinguish cannabis from Australia, Papua New Guinea and Thailand, while separating conditions within one site. The later models for regions of the United States, built on hydrogen and carbon values and a large set of specimens of recorded origin, were right for 60 to 67 per cent of specimens tested blind.
What the measurement is for. Denton and colleagues propose nitrogen values for matching a seized sample to a particular crop, a comparison between two samples. The United States work assigns a sample to a region of origin by model. The two claims differ in kind.
Bulk tissue or single compounds. Bulk carbon values separated five samples where values measured on the extracted cannabinoids did not separate one pair. Muccio and colleagues call for further work on how far the cannabinoids are fractionated relative to the tissue, above all in aged material.
How far a spectral model reaches. Both infrared studies report high accuracy within their own sample sets, 95 per cent and 100 per cent for the two places in one and the best of four models in the other. Both sort samples among the places whose material trained them, and the Indian study describes itself as a proof of concept.

How far the evidence goes

The samples of known origin in these studies are material taken by police: plants from eradicated gardens recorded by county, consignments stopped at borders and retail seizures. The regions the models separate are the regions those samples came from.
The reliability figures belong to the specimen sets tested. The 60 to 67 per cent and 86 per cent figures are for 60 eradication specimens of the United States; the Brazilian and Colorado accuracies are for 47 and 18 samples.
The strontium comparison of 2009 is against a modelled map of bedrock values, not against measurements of the ground at each site.
The hemp work of Italy and Iceland was done on the crop grown for food and fibre, and the Icelandic study rests on one soil type across a single island.
The thresholds separating plant-derived from synthesised cannabidiol come from one study and are stated at a confidence level of 95 per cent.
Carbon values below the range of field-grown plants point to the air the plants were given. Twelve of the Alaskan samples ran from −36.1 to −61.8 parts per thousand.

Terms

Parts per thousand: isotope ratios are reported as the difference from a standard, in parts per thousand, written with the delta symbol in the sources (δ¹³C, δ¹⁵N, δ²H or δD, δ¹⁸O).
⁸⁷Sr/⁸⁶Sr: the strontium ratio, reported as a plain number rather than as a difference from a standard.
Attenuated total reflectance: the sampling arrangement used for the infrared spectra in both of the spectral studies, in which the material is pressed against a crystal.
Isoscape: a map of expected isotope values across a territory, against which a sample's value is compared.
Reference material: material whose origin is recorded, measured to give the values a sample is compared with.

Images reserved in the article

One image has a place in the article but is not yet uploaded:

File:Cannabis-origin-signals-diagram.jpg (lead), a diagram to be drawn: a dried cannabis sample with five arrows to what each measurement records, labelled "Carbon and nitrogen: the conditions the plant grew in, among them water, shade and fertiliser", "Hydrogen and oxygen: the water the plant used", "Strontium: the rock beneath the field", "Infrared spectrum: the chemical make-up of the dried material" and "Mineral elements: what the plant took up from the ground", with a band across the foot reading "A reading places a sample only against measurements of material whose origin is known". No map, no place names and no accuracy figures.