How hair opens up new strands of toxicological analysis

Her body was discovered by authorities in July, when the odour of decomposition prompted reports that something was amiss in an Osaka, Japan residence. An investigation ensued to determine the cause of death.¹ Autopsy findings included no observable signs of external trauma, disease or injury that contributed to death, which was estimated to have occurred approximately two months previously. While ‘no evidence was found indicating the use of illicit drugs’, scattered around the deceased woman were thousands of empty blister packs for sleep-inducing drugs.

Investigators determined she had been prescribed ‘a large quantity’ of said drugs ‘from multiple clinics for the treatment of insomnia’ in the months leading up to her death. The majority of the empty packs were the sedative-hypnotics zolpidem (Ambien) and brotizolam (Lendormin).

While conventional toxicological analysis of blood and urine samples could reveal the role these drugs played in this death, such analysis was not an option in this case. The approximate two month time span between death and its discovery – the postmortem interval – meant decomposition precluded the necessary sample collection, as ‘no blood or urine suitable for toxicological analysis remained in the body.’¹ Analysts turned to another sample type known for ‘its ability to retain incorporated drugs or poisons over extended periods’ – hair.

Combing for evidence

Hair is an important sample type for a variety of forensic science disciplines, from DNA to toxicology.² Analysis of hairs for controlled substances has a long history, with Annette Baumgartner and colleagues’ work in the late 1970s assessing opiates in human hair segments via radioimmunoassay described as a pivotal advance.^3–6 Hair samples both complement any blood and urine samples that are available for toxicological analysis and can expand the analytical view.

Compared to the hours-to-days view blood and urine analysis can provide, hair analysis can offer a larger surveillance window.^1,2,4–8 Depending on hair length, composition and condition – plus the specific controlled substance – toxicological analysis of hair can provide long-term histories of controlled substance exposures of weeks-to-months and beyond.

Interpreting hair concentrations of controlled substances is complex, but careful research and development is boosting the quantitative capabilities of hair analysis while confirming its qualitative prowess.

Drug analysis methods featuring liquid chromatography with tandem mass spectrometry (LC–MS/MS) have emerged as a gold standard in forensic toxicology for hair, providing high sensitivity and selectivity of a range of drugs.² By evaluating ever-smaller segments of hair via LC–MS/MS, investigators can break down exposure timelines into ever-finer time increments.

Cutting into ever finer segments

In 2016, Kenji Kuwayama and colleagues introduced a segmental hair analysis technique that examined strands at 0.4mm intervals, ‘corresponding to a hair growth length of approximately one day.’⁴ Continued development of millimetre-scale hair segment analysis via LC–MS/MS is enabling analysts to meet forensic toxicological challenges, including within death investigations involving ‘highly decomposed corpses’ such as the aforementioned Osaka case.

In this case, a team of experts from Osaka Medical and Pharmaceutical University’s department of legal medicine and Osaka Prefectural Police’s forensic science laboratory employed their previously established ultra-high-sensitivity LC–MS/MS method for millimetre-scale hair segmental analysis to ascertain the role the decedent’s insomnia treatments played in her death. Besides zolpidem and brotizolam, other drugs prescribed to her included flunitrazepam, lemborexant and quetiapine. Qualitative LC–MS/MS analysis of hair root and shaft segments confirmed the presence of all five prescribed drugs, with 10mm interval segmental hair analysis starting from the root of the hair revealing ‘a relatively uniform distribution for all five drugs, suggesting regular use over a period of at least 6 months prior to death.’¹

Quantitative work and careful consideration of revelant previously published toxicological studies led the Osaka team to exclude ‘acute overdose’ or ‘excessive’ ingestion immediately before death for each of the five aforementioned drugs. The earlier autopsy revealed no clear cause of death and meticulous analysis by the Osaka team excluded acute drug poisoning, leading to the cause of death being classified as undetermined.

Advances in analytical chemistry can provide answers even while a mystery remains.