Pretreatment methods of pollen grains on clothing and in surface soil samples for LM and SEM observation in forensic palynology

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K21060
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 25:Social systems engineering, safety engineering, disaster prevention engineering, and related fields
• Research Institution: Kochi University
• Principal Investigator: MIYAKE Nao 高知大学, 教育研究部自然科学系理工学部門, 准教授 (60294823)
• Project Period (FY): 2020-07-30 – 2024-03-31
• Keywords: 花粉標本作製法 / 検査法マニュアル / 走査型電子顕微鏡 / 証拠物件資料 / 法花粉学的検査法

Outline of Final Research Achievements

Pollen grains on clothing and in surface soil samples, applied different methods of pretreatment to, were observed via light microscopy (LM) and scanning electron microscopy (SEM) in terms of forensic palynology. The combination of KOH and acetolysis methods was the most suited for pollen identification using LM. For detailed morphological comparisons and taxonomy of pollen using SEM, the standard palynological pretreatment (heavy metal coating with successive pretreatments of KOH, acetolysis and osmium tetroxide) was more appropriate in the case that there were enough time and sample volume. In other cases, heavy metal coating without pretreatment, ionic liquid, or NanoSuit methods were more effective. Especially, the NanoSuit method is expected to be used for SEM observation of pollen, because it was simpler and more rapid than other pretreatment methods, and pollen sculpture could be observed in a near non-treated state under high-vacuum condition.

Free Research Field

古生態学，花粉学

Academic Significance and Societal Importance of the Research Achievements

法花粉学は，法花粉学的検査が実際に事件解決に寄与した研究事例の蓄積をもとに発展してきた．しかも，これらの事例での検査法の記述が不明瞭で，検査法自体や検査データの解釈の妥当性の検証が困難なものも少なくない．本研究では，土壌表層・衣服資料を対象とし，検査試料から必要な花粉情報を得るための合理的，効率的な処理法を構築・体系化した．本研究を通して，現場捜査官や検査者の検査法に対する正しい理解を促し，法花粉学を志向する初学者の分野理解や育成を図ることで，司法制度への応用を通じ犯罪解決に貢献できる．