Is insulin intoxication still the perfect crime? Analysis and interpretation of postmortem insulin: review and perspectives in forensic toxicology

A retrospective study of 29 fatal cases of insulin overdose

PURPOSE

To summarize recent cases of fatal insulin poisoning both domestically and internationally, thereby offering valuable insights for the forensic identification of insulin overdose cases.

METHODS

Literature published since 2000 on fatal insulin overdose were systematically searched and screened. Data encompassing variables such as year, age, sex, cause of death, scene conditions, occupations, medical histories of victims and perpetrators, autopsy timing, dosage and administration methods, forensic pathology, and toxicological analysis, were compiled for rigorous statistical analysis.

RESULTS

Among the 29 fatal cases of insulin poisoning, suicides and homicides accounted for 55.2 % and 41.4 %, respectively. Precisely 34.5 % of victims or perpetrators were associated with the medical industry, 27.6 % had diabetes, and 24.1 % had mental illnesses such as depression. Intravenous injection resulted in quicker death than did subcutaneous injection. In some cases, immunohistochemical staining of insulin and protamine at injection sites yielded positive results. The average molar ratio of insulin to C-peptide in post-mortem blood was 13.76 ± 5.167, indicating a significant diagnostic value for insulin poisoning.

CONCLUSION

Assessment of cases of fatal insulin overdose should be thorough, incorporating case investigation, scene examination, medical records review, autopsy findings, pathological examinations, and laboratory tests, alongside considering the condition of the body and timing of death autopsy. Using mass spectrometry to detect insulin proves valuable, particularly in cases of poor body preservation.

Is it really possible to kill with insulin without leaving traces? From lifesaver to killer, the issues surrounding the analytical characterization of postmortem insulin illustrated by an exemplary case

Evidence of an insulin overdose is very complicated in the medico-legal field. The analysis and subsequent interpretation of results is complex, especially when treating postmortem blood samples. The instability of insulin, the special pre-analytical conditions and the absence of specific analytical methods has led most laboratories not to analyze insulin in their routine with a consequent underestimation of cases. This paper aims to assess the difficulties associated with the analytical characterization of insulin by describing a case that typically represents most of the inconveniences encountered following a suspected insulin overdose. The case concerns a man found dead at home by his brother. After an external examination, which did not reveal a specific cause of death, toxicological analysis was requested which did not reveal any substance of toxicological interest. Only 9 months later, it was reported to the toxicologist that the subject was diabetic, on insulin lispro treatment and that three empty syringes were found next to his body. Following analysis by LC-high-resolution mass spectrometry, the presence of insulin lispro at a concentration of 1.1 ng/mL, a therapeutic concentration, was evidenced. Despite the low concentration found, overdose cannot be excluded and this paper will describe the criteria evaluated to reach this conclusion. This case highlights that the interpretation of a postmortem insulin concentration is very complex and requires the evaluation of various elements including the circumstances of death, the subject's medical history, the interval between death and sampling and the sample storage.

Biochemical Toxicological Study of Insulin Overdose in Rats: A Forensic Perspective

Due to nonspecific pathological changes and the rapid degradation of insulin in postmortem blood samples, the identification of the cause of death during insulin overdose has always been a difficulty in forensic medicine. At present, there is a lack of studies on the toxicological changes and related mechanisms of an insulin overdose, and the specific molecular markers of insulin overdose are still unclear. In this study, an animal model of insulin overdose was established, and 24 SD rats were randomly divided into a control group, insulin overdose group, and a recovery group (n = 8). We detected the biochemical changes and analyzed the toxicological mechanism of an insulin overdose. The results showed that after insulin overdose, the rats developed irregular convulsions, Eclampsia, Opisthotonos, and other symptoms. The levels of glucose, glycogen, and C-peptide in the body decreased significantly, while the levels of lactate, insulin, and glucagon increased significantly. The decrease in plasma K+ was accompanied by the increase in skeletal muscle K+. The PI3K-AKT signaling pathway was significantly activated in skeletal muscle, and the translocation of GLUT4/Na+-K+-ATPase to sarcolemma was significantly increased. Rare glycogenic hepatopathy occurred in the recovery group after insulin overdose. Our study showed that insulin overdose also plays a role in skeletal muscle cells, mainly through the PI3K-Akt signaling pathway. Therefore, the detection of signaling pathway proteins of the skeletal muscle cell membrane GLUT4 and Na+-K+-ATPase has a certain auxiliary diagnostic value for forensic insulin overdose identification. Glycogen detection in the liver and skeletal muscle is important for the diagnosis of insulin overdose, but it still needs to be differentiated from other causes of death. Skeletal muscle has great potential for insulin detection, and the ratio of insulin to the C-peptide (I:C) can determine whether an exogenous insulin overdose is present.

Immunohistochemical detection of insulin at the injection site in a case of suspected murder with the suicide of the perpetrator

In medicolegal practice, rare cases involving suicidal, criminal, or accidental insulin overdose are both analytically and forensically challenging. The aim of this study is to present a model procedure in such cases, developed at the Department of Forensic Medicine and Toxicology of the Medical University of Silesia in Katowice, with particular emphasis on the possibility of additional confirmation of insulin intake by its immunohistochemical detection at the injection site. In the example case presented here, an immunohistochemical examination using FLEX Polyclonal Guinea Pig Anti-Insulin antibody (code IR002, Dako) confirmed the presence of insulin in the subcutaneous tissue of the victims. In our opinion, the method of immunohistochemical detection of insulin at the injection site can and should be used routinely in such cases. Immunohistochemiczna detekcja insuliny w miejscu wkłucia w przypadku podejrzenia zabójstwa z samobójstwem sprawcy W praktyce medyczno-sądowej przypadki związane z samobójczym, zbrodniczym lub przypadkowym przedawkowaniem insuliny są rzadkie i należą do trudnych pod względem analitycznym i opiniodawczym. Celem pracy jest przedstawienie modelowego postępowania w tego typu przypadkach opracowanego w Katedrze i Zakładzie Medycyny Sądowej i Toksykologii Sądowo-Lekarskiej w Katowicach, ze szczególnym uwzględnieniem możliwości dodatkowego potwierdzenia podania insuliny przez jej immunohistochemiczną detekcję w miejscu wkłucia. W zaprezentowanym przypadku badanie immunohistochemiczne z wykorzystaniem przeciwciała Polyclonal Guinea Pig Anti-Insulin FLEX IR002 (Dako) potwierdziło obecność insuliny w tkance podskórnej obu ofiar. Naszym zdaniem metoda immunohistochemicznej detekcji insuliny w miejscu wkłucia może i powinna być stosowana w każdym tego rodzaju przypadku.

Insulin murder and the case of Colin Norris

Although insulin is an essential medicine and a life-saving drug, it has also been incriminated in many poisoning deaths; accidental, suicidal and some with malicious intent. Overdosing with insulin precipitates a life-threatening state of hypoglycemia and if untreated leads to coma, irreversible brain damage and death. Normally, the pancreatic β-cells secrete equimolar amounts of insulin and C-peptide into the portal venous blood, although under physiological conditions the plasma concentration ratio (insulin/C-peptide) is less than unity, because insulin is more susceptible to hepatic first-pass metabolism. A high ratio of insulin/C-peptide in plasma from a poisoned patient is compelling evidence that pharmaceutical insulin was administered, which does not contain C-peptide. The analysis of insulin and C-peptide was traditionally done by immunoassay methods (RIA and/or ELISA), although high resolution LC-MS/MS is more suitable for forensic purposes and permits the identification of insulin analogues. Use of insulin as a murder weapon is exemplified by the case of Colin Norris, a male nurse found guilty of murdering four elderly patients and the attempted murder of a fifth by injecting them with insulin. However, the prosecution evidence against Norris was mainly circumstantial and hearsay. Toxicological evidence against Norris consisted of a high insulin/C-peptide concentration ratio in plasma from one of the victims. This analysis was done by an immunoassay method at a clinical laboratory and not a forensic laboratory. Analytical procedures, including chain-of-custody routines, are more stringent at forensic laboratories. Since his conviction, some of the medical evidence against Norris has been called into question, especially the prevalence of spontaneous attacks of hypoglycemia in elderly and frail patients with co-morbidities.

Postmortem Metabolomics of Insulin Intoxications and the Potential Application to Find Hypoglycemia-Related Deaths

Postmortem metabolomics can assist death investigations by characterizing metabolic fingerprints differentiating causes of death. Hypoglycemia-related deaths, including insulin intoxications, are difficult to identify and, thus, presumably underdiagnosed. This investigation aims to differentiate insulin intoxication deaths by metabolomics, and identify a metabolic fingerprint to screen for unknown hypoglycemia-related deaths. Ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry data were obtained from 19 insulin intoxications (hypo), 19 diabetic comas (hyper), and 38 hangings (control). Screening for potentially unknown hypoglycemia-related deaths was performed using 776 random postmortem cases. Data were processed using XCMS and SIMCA. Multivariate modeling revealed group separations between hypo, hyper, and control groups. A metabolic fingerprint for the hypo group was identified, and analyses revealed significant decreases in 12 acylcarnitines, including nine hydroxylated-acylcarnitines. Screening of random postmortem cases identified 46 cases (5.9%) as potentially hypoglycemia-related, including six with unknown causes of death. Autopsy report review revealed plausible hypoglycemia-cause for five unknown cases. Additionally, two diabetic cases were found, with a metformin intoxication and a suspicious but unverified insulin intoxication, respectively. Further studies are required to expand on the potential of postmortem metabolomics as a tool in hypoglycemia-related death investigations, and the future application of screening for potential insulin intoxications.

Insulin and Oral Hypoglycemic Drug Overdose in Post-Mortem Investigations: A Literature Review

Background and Objectives: Insulin and oral hypoglycemic agents are drugs widely used in the world population due to their therapeutic effects on diabetes mellitus. Despite these benefits, they can also cause accidental or voluntary drug overdose. This review aims to evaluate post-mortem investigations in cases of suspected hypoglycemic drug overdose. Materials and Methods: We performed a comprehensive search using the Preferred Reporting Items for Systematic Review (PRISMA) standards; we systematically searched the PubMed, Science Direct Scopus, Google Scholar, and Excerpta Medica Database (EM-BASE) databases from the point of database inception until August 2022. The following inclusion criteria were used: (1) original research articles, (2) reviews and mini-reviews, (3) case reports/series, (4) and only papers written in English. Results: Thirty-three scientific papers, including original research articles, case reports, and case series, fulfilled the inclusion criteria. A total of 109 cases of insulin or hypoglycemic drug overdose were found. There were 71 cases of suicide (65%), 25 cases of accidental poisoning (23%), and 13 cases of homicide (12%). The most commonly used drug was insulin (95.4%). Autopsy and post-mortem examinations were performed in 84 cases, while toxicological investigations were performed in 79 cases. The most common gross findings in the autopsy were pulmonary edema (55.7%) and congestion (41.8%), while the most common histological finding was neuronal depletion or necrosis (29.1%). Conclusions: In the suspicion of death from insulin or overdose from oral hypoglycemic agents, autopsy findings may be nonspecific, and the search for injection marks can be positive at the external examination. Significant post-mortal alterations can interest biological samples and an early autopsy investigation is recommended.

Poisoning cases in the German crime series Tatort (crime scene) from 1974 to 2022

Poisoning occurs frequently in TV crime series but, to the best of our knowledge, has not yet been analyzed scientifically. This study examines the plausibility of poisoning cases in Germany’s most popular crime series, Tatort (crime scene), from 1974 to 2022. In the TV series, the increasing rate of poisoning in Germany as well as the increasing variety of substances leading to poisoning over the years are depicted. Largely in line with reality, similar substance categories and routes of administration are presented. However, poisoning outcomes in Tatort differ from reality: over 50% of the victims die in Tatort, whereas in reality, more than 80% survive. In > 95% of the episodes, the mechanism of action of a poison is not explained, omitting an important opportunity for raising public awareness. The TV series also deviates from reality in terms of the etiology of poisonings: External poison delivery is largely overrepresented, while the high rate of accidental poisonings in real life is underrepresented. Almost no accidental poisonings occur in Tatort, although this is the most frequent type of poisoning in real life. In Tatort, men are overrepresented as offenders and victims of poisoning compared to reality. Thus, the crime series does not convey the message that anyone can be a potential victim of poisoning and that particularly vulnerable groups need proper education and the best possible protection. This paper discusses the conflict between detailed, plausible episodes with cases of poisoning and the potential for imitation that they may cause.

Detection of insulins in postmortem tissues: an optimized workflow based on immunopurification and LC-MS/HRMS detection

Diabetes is a worldwide disease in perpetual expansion. Type 1 and sometimes type 2 diabetic patients require daily human insulin (HI) or analog administration. Easy access to insulins for insulin-treated diabetics, their relatives, and medical professionals can enable abuse for suicidal or homicidal purpose. However, demonstrating insulin overdose in postmortem blood is challenging. Tissue analyses are contributive, as insulins can accumulate before death or undergo only limited degradation. The present study describes an assay for HI and synthetic analogs (lispro, aspart, glulisine, detemir and degludec, glargine and its main metabolite (M1)) in liver, kidney, muscle, and injection site samples. It is based on a 5-step sample preparation (reduction of tissue sample size, homogenization, extraction, concentration, and immunopurification) associated with liquid chromatography coupled to high-resolution mass spectrometry (LC-MS/HRMS). Selectivity and limit of detection (LOD) for all target analogs were assessed in the above matrices. LOD was determined at 25 ng/g for HI and for analogs except detemir and degludec, where LOD was 50 ng/g in kidney and injection site samples and 80 ng/g in the liver and muscle. The method was applied to13 forensic cases in which insulin use was suspected.

Development and validation of a method for quantification of human insulin and its synthetic analogues in plasma and post-mortem sera by LC-MS/HRMS

Analysis of human insulin and its synthetic analogues is increasingly requested for clinical monitoring, for anti-doping purposes, but also for forensic cases. Indeed, insulin analogues may be abused for suicide or homicide - whence their forensic interest. Collection and storage conditions, as well as the phenomenon of degradation make post-mortem serum samples analytically challenging and consequently, the rate of exogenous insulin administration as cause of death is undoubtedly underestimated. However, with recent technological advances and the development of new extraction techniques particularly for anti-doping analyses, detection of insulins in post-mortem samples seems to be achievable. This study describes the first validated quantitative method for analysis human insulin and its six analogues (lispro, aspart, glulisine, glargine, detemir and degludec) in plasma and post-mortem sera. Various extraction processes, namely precipitation + solid phase extraction (SPE), filtration + SPE, precipitation + SPE + immunopurification, and filtration + immunopurification, were assessed to evaluate the lowest limit of detection for all target analogues. The selected sample preparation consists of filtration step followed by immunopurification extraction with an anti-body precoated ELISA plate for plasma. For post-mortem sera, the first step of precipitation was added to remove matrix interferences. The extracts were analyzed by ultra-high-performance liquid chromatography-high resolution mass spectrometry (LC-HRMS), interfaced by electrospray (ESI). The method was validated with respect linearity, precision, accuracy, recovery, matrix effect, dilution and carryover. The limit of quantification (LOQ) in plasma was 0.5 ng/mL for human insulin and rapid-acting insulins, 1.0 ng/mL for glargine, 2.5 ng/mL for degludec and 10 ng/mL for detemir. Two types of post-mortem sera were studied based on the post-mortem interval (PMI): inferior or superior to 48 h. The obtained LOQ were the same for each analogue, independent from the PMI: 1.0 ng/mL for human insulin and rapid-acting insulins, 1.0 ng/mL for glargine, 2.5 ng/mL for degludec and 10 ng/mL for detemir. At the LOQ level, for all insulins and all samples, accuracy was between 70 and 130% and precision inferior to 30%. The validated method was applied to five subjects participating in therapeutic monitoring of insulin and to seven post-mortem cases.