Natural Traces in forensic investigations - How pollen imprints can solve crime: Review of the open-access literature on forensic palynology

This research is developed within the Horizon Europe 2020 MSCA Doctoral Network ‘Natural Traces’ project (Grant number: 101120165) dealing with the use of non-human biological traces in forensic science. Forensic palynology is a branch of palynology, the study of pollen grains, that focuses on its implementation in criminal investigations giving microbotanical evidences. Pollen analysis could provide information on the vegetation cover and representation of different plant species in a crime scene, often providing a direct link between objects, people, and places that may pertain to criminal cases. Non-pollen palynomorphs (e.g., fungal spores, algal elements, other microremains of biological origin) that can be observed on the palynological slides are able to give important and additional information about the ecology of the sampling site. The PhD project is aimed at i) studying existing forensic palynological literature, ii) finding and testing methods used in them and iii) modifying some of these protocols to develop the most effective, simple and not expensive in performance methods of sampling and pollen and non-pollen palynomorphs extraction that will work with the most common types of materials and allow crime scene investigators to implement it into an everyday practice. Within this research project, a literature review has been undertaken; this report presents some information got from the search on the 159 open-accessed literature sources (as of May 2025). The review was made for the articles which were published in the time period from 1971 to 2025. The literature research was made in databases of Scopus, ResearchGate and BASE (Bielefeld Academic Search System) with criteria: "forensic palynology"; "forensic AND palynology"; "forensic AND pollen"; "crime AND pollen"; "crime AND palynology” resulted in 160, 101 and 297 findings respectively. The most actively published years for forensic palynology started in 2006. There were found 58 papers that were based on the real cases, 68 sources that were based on the experiments and 33 articles that were reviews. Real cases were associated mainly with homicide, robbery, drug abuse, contrafacts, archaeoforensics, rape, etc. The most published papers were found from the UK, USA, Italy, New Zealand and India. Sampling methods were mainly represented by collecting materials, washing, brushing, swabbing the examined materials and surfaces. The most used methods of chemical treatment of samples were Faegri and colleagues’ method (1), Erdtman’s acetolysis (2) and von Post’s method (3). Further steps of the project will be focused on the methodological aspects of palynological researches studied in the represented literature and their effectiveness of pollen extraction from the different materials. 1) K. Faegri, P. E. Kaland, K. Krzywinski (1989) Textbook of pollen analysis. 4th edn. Caldwell, Blackburn Press 2) G. Erdtman (1960) The acetolysis method: a revised description. Svensk Bot. Tidskr, 54, 561 3) L. von Post (1916) Einige südschwedischen Quellmoore. Bull. Geol. Inst. Univ. Upsala, 15, 219-278