Postmortem computed tomography (PMCT) and disaster victim identification.

Radiography has been used for identification since 1927, and established a role in mass fatality investigations in 1949. More recently, postmortem computed tomography (PMCT) has been used for disaster victim identification (DVI). PMCT offers several advantages compared with fluoroscopy, plain film and dental X-rays, including: speed, reducing the number of on-site personnel and imaging modalities required, making it potentially more efficient. However, there are limitations that inhibit the international adoption of PMCT into routine practice. One particular problem is that due to the fact that forensic radiology is a relatively new sub-speciality, there are no internationally established standards for image acquisition, image interpretation and archiving. This is reflected by the current INTERPOL DVI form, which does not contain a PMCT section. The DVI working group of the International Society of Forensic Radiology and Imaging supports the use of imaging in mass fatality response and has published positional statements in this area. This review will discuss forensic radiology, PMCT, and its role in disaster victim identification.

Post-mortem computed tomography ventilation; simulating breath holding.

Whilst the literature continues to report on advances in the use of post-mortem computed tomography (PMCT), particularly in relation to post-mortem angiography, there are few papers published that address the diagnostic problems related to post-mortem changes in the lungs and ventilation. We present a development of previous methods to achieve ventilated PMCT (VPMCT). We successfully introduced a supraglottic airway in 17/18 cases without causing overt damage, despite rigor mortis. Using a clinical portable ventilator, we delivered continuous positive airway pressure to mimic clinical breath-hold inspiratory scans. This caused significant lung expansion and a reduction in lung density and visible normal post-mortem changes. All thoracic pathology identified at autopsy, including pneumonia, was diagnosed on VPMCT in this small series. This technique provides a rapid form of VPMCT, which can be used in both permanent and temporary mortuaries, allowing for the post-mortem radiological comparison of pre-ventilation and post-ventilation images mimicking expiratory and inspiratory phases. We believe that it will enhance the diagnostic ability of PMCT in relation to lung pathology.

Adult post-mortem imaging in traumatic and cardiorespiratory death and its relation to clinical radiological imaging.

The use of post-mortem imaging is expanding throughout the world with increasing use of advanced imaging techniques, such as contrast-enhanced CT and MRI. The questions asked of post-mortem imaging are complex and can be very different, for example for natural sudden death investigation will focus on the cause, whereas for trauma the cause of death is often clear, but injury patterns may be very revealing in investigating the background to the incident. Post-mortem imaging is different to clinical imaging regarding both the appearance of pathology and the information required, but there is much to learn from many years of clinical research in the use of these techniques. Furthermore, it is possible that post-mortem imaging research could be used not only for investigating the cause of death but also as a model to conduct clinically relevant research. This article reviews challenges to the development of post-mortem imaging for trauma, identification and cardiorespiratory death, and how they may be influenced by current clinical thinking and practice.

The role of micro-computed tomography in forensic investigations.

The use of micro-CT within forensic practice remains an emerging technology, principally due to its current limited availability to forensic practitioners. This review provides those with little or no previous experience of the potential roles of micro-CT in forensic practice with an illustrated overview of the technology, and the areas of practice in which micro-CT can potentially be applied to enhance forensic investigations.

Accuracy of targeted post-mortem computed tomography coronary angiography compared to assessment of serial histological sections.

Post-mortem computed tomography with coronary angiography (PMCTA) could have a role in the investigation of sudden natural death. This study assesses the accuracy of targeted coronary PMCTA, using both air and iodinated contrast media, to provide sensitivity and specificity for critical stenosis (CS) on a segmental basis, based on a gold standard of 3-5 mm serial sections of the coronary arteries using macroscopic and histological techniques. Assessment of stenosis at 1 mm intervals on PMCTA was compared with the data from pathological analysis. Stenosis was defined as "critical" when the stenotic region reaches ≥75 %. Regions were defined every 20 mm or by a clear change in stenosis. Discrepancies were defined as significant if only one test showed CS. Five cases with 25 vessels with 124 regions were assessed. PMCTA was unable to identify plaque hemorrhage or dissection (but this was normally associated with CS). Eighteen segments had significant discrepancies, giving a sensitivity and specificity of 50 and 91.5 %. When an alternative gold standard was constructed by excluding regions beyond a CS (five cases), taking PMCTA as correct where a heavily calcified vessel opens under contrast injection (four cases), and correcting for misregistration of distance (one case), the sensitivity rose to 85.7 %. There was complete agreement when the right or left coronary arteries are assessed as a whole. This study shows that PMCTA is not a perfect replacement for histological examination of coronary vessels, but may have a role in routine post-mortem investigation.

The effect on toxicology, biochemistry and immunology investigations by the use of targeted post-mortem computed tomography angiography.

It is recognised in autopsy practice that investigations such as toxicology can be affected by post-mortem change. Post-mortem computed tomography angiography (PMCT-A) involves the injection of contrast agents. This could cause dilution of a biological fluid sample or cause the circulation of blood after death by mechanical pumping, and thus has the potential to affect laboratory investigations. We undertook a small sample study to consider whether targeted PMCT-A had any significant effect on subsequent samples taken for biochemical, toxicological or immunological investigations. Although the results of our study do illustrate differences between the pre and post PMCT-A results, these differences are considered not to be of diagnostic significance and not due to the direct effect of targeted PMCT-A.

The criminal justice system's considerations of so-called near-virtual autopsies: the East Midlands experience.

BACKGROUND: While several research groups champion the potential for postmortem CT (PMCT) to replace the invasive postmortem (PM), many questions still remain. AIMS: Perhaps the two most important questions are whether PMCT can provide the same level of information as an invasive PM, and arguably more importantly, can it meet the needs of the end users of the PM report. Through a comparative analysis of invasive post-mortem and CT findings and a questionnaire based qualitative thematic analysis, the authors have sought to answer these questions. RESULTS AND CONCLUSION: Here, the authors show that PMCT is good at providing accurate causes of death and that the interpretation of cases is not significantly altered by the absence of histology. The authors show that in straightforward trauma deaths such as road traffic incidents, there exists the potential for the replacement of the invasive PM by PMCT examination. However, as yet, PMCT cannot provide all of the information that is expected by the criminal justice system in complex forensic cases.

The use of post-mortem computed tomography in the investigation of intentional neonatal upper airway obstruction: an illustrated case.

We present a single case report illustrating the diagnostic role of multi-slice computed tomography (MSCT) in the investigation of suspicious child death where mechanical asphyxia is suspected. The case illustrates how radiological findings that may not be observable on conventional plain X-ray were identified by post-mortem MSCT. We illustrate how MSCT can illustrate the position of a foreign body within the upper airway of a neonate without the need for in situ dissection and how the combination of post-mortem MSCT with skeletal survey can provide enhanced diagnostic information in the investigation of not only whether the child was liveborn but also the consideration as to whether or not death has been caused by upper airway obstruction.

Methadone toxicity in infants: a report of two fatalities.

Fatalities in infants resulting from methadone toxicity are rare within the United Kingdom. We report two cases of fatality attributed to methadone toxicity in infants aged 3(1/2) and 15 months of age, respectively. One of the two cases was also associated with diazepam ingestion. We discuss the difficulties with the interpretation of paediatric forensic toxicology and review the current literature related to methadone and diazepam toxicity in infants and older children.

Room temperature DNA preservation of soft tissue for rapid DNA extraction: an addition to the disaster victim identification investigators toolkit?

In mass fatality incidents, for example following a vehicle accident or terrorist event, severe fragmentation of bodies may occur, making identification by the use of traditional techniques such as fingerprinting or odontology difficult. In such situations DNA profiling can be employed for individualization and re-association of fragmented remains. As at times disrupted soft tissue may be the predominate tissue type requiring identification and re-association. We have investigated the use of two buffer solutions for preservation of soft tissue samples that may be collected during such investigations, when buccal cells, blood samples or teeth or bone may not be available. Both buffer solutions have shown sufficient DNA preservation over a 12-month period of storage at room temperature to allow for DNA profiling to be successfully performed when 5-1000 mg muscle tissue was stored in each solution.

Computed tomography of projectile injuries.

Computed tomography (CT) is a gold standard in clinical imaging but forensic professions have been slow to embrace radiological advances. Forensic applications of CT are now exponentially expanding, replacing other imaging methods. As post-mortem cross-sectional imaging increases, radiologists will fall under increasing pressure to interpret complex forensic cases involving both living and deceased patients. This review presents a wide variety of weapon and projectile types aiding interpretation of projectile injuries both in forensic and clinical practice.

Retrieval of DNA from the faces of children aged 0-5 years: a technical note.

Approximately 21% of children suffer from some form of physical abuse. It is hypothesized that when an individual hits a child some of that person's DNA will be deposited onto the child's skin. As yet, no one has reported a method of sampling DNA from the skin of this vulnerable group of individuals. We have sampled DNA from several facial areas of 30 children aged 5 years of age and under. The results show that it is possible to swab the faces of this age group without distressing them or contaminating the samples. Additionally the results indicate that the DNA obtained is almost entirely that of the subject, with little nondonor DNA being observed.

Can cause of death be predicted from the pre-necropsy information provided in coroners' cases?

AIM: To determine whether the cause of death can be accurately predicted from the pre-necropsy information available in coroners' cases, before carrying out a postmortem examination. METHODS: In this prospective study pathologists read the clinical summary provided by the Coroner's Office and formulated a predicted cause of death. An external examination was then conducted and any relevant information recorded, together with any changes to the original predicted cause of death. They then carried out a complete necropsy before recording a final cause of death, which was subsequently compared with their prediction. RESULTS: A total of 95 necropsies were included in the study. The cause of death was deemed to have been correctly predicted from the history in 62 cases (65.3%). In 33 cases (34.7%) an unexpected cause of death was found. Findings from the external examination were noteworthy in only 8 cases (8.4%), and did not alter the cause of death in any case. CONCLUSIONS: In certain circumstances an accurate cause of death may be given with confidence without the apparent need for necropsy. However, many common causes of death can present with similar or misleading scenarios. This study indicates that performing necropsies, despite seemingly predictable circumstances, is advisable if an accurate cause of death is to be recorded.

The role of computed tomography in terminal ballistic analysis.

Terminal ballistics concerns the science of projectile behaviour within a target and includes wound ballistics that considers what happens when a projectile strikes a living being. A number of soft tissue ballistic simulants have been used to assess the damage to tissue caused by projectiles. Standard assessment of these materials, such as ballistic soap or ordnance gelatine, requires the block to be opened or that a mould to be made to visualize the wound track. This is time consuming and may affect the accuracy of the findings especially if the block dries and alters shape during the process. Therefore, accurate numerical analysis of the permanent or temporary cavity is limited. Computed tomography (CT) potentially offers a quicker non-invasive analysis tool for this task. Four commercially purchased ballistic glycerine soap blocks were used. Each had a single firearm discharged into it from a distance of approximately 15 cm using both gunshot and shotgun projectiles. After discharge, each block was imaged by a modern 16 slice multi-detector CT scanner and analysed using 3-D reconstruction software. Using the anterior-posterior and lateral scout views and the multi-plane reconstructed images, it was possible to visualize the temporary cavity, as well as the fragmentation and dispersal pattern of the projectiles, the distance travelled and angle of dispersal within the block of each projectile or fragment. A virtual cast of the temporary cavity can be also be made. Multi-detector CT with 3-D analysis software is shown to create a reliable permanent record of the projectile path allowing rapid analysis of different firearms and projectiles.

How sharp is sharp? Towards quantification of the sharpness and penetration ability of kitchen knives used in stabbings.

Stabbing is the most common method for violent death in the UK. As part of their investigation, forensic pathologists are commonly asked to estimate or quantify the degree of force required to create a wound. The force required to penetrate the skin and body by a knife is a complex function of the sharpness of the knife, the area of the body and alignment with cleavage lines of the skin, the angle of attack and the relative movement of the person stabbing relative to the victim being stabbed. This makes it difficult for the forensic pathologist to give an objective answer to the question; hence, subjective estimations are often used. One area where some degree of quantification is more tractable is in assessing how sharp an implement (particularly a knife) is. This paper presents results of a systematic study of how the different aspects of knife geometry influence sharpness and presents a simple test for assessing knife sharpness using drop testing. The results show that the radius of the blunt edge at the tip is important for controlling the penetration ability of a kitchen knife. Using high-speed video, it also gives insight into the mechanism of knife penetration into the skin. The results of the study will aid pathologists in giving a more informed answer to the question of the degree of force used in stabbing.

Electronic fingerprinting of the dead.

To date, a number of methods exist for the capture of fingerprints from cadavers that can then be used in isolation as a primary method for the identification of the dead. We report the use of a handheld, mobile wireless unit used in conjunction with a personal digital assistant (PDA) device for the capture of fingerprints from the dead. We also consider a handheld single-digit fingerprint scanner that utilises a USB laptop connection for the electronic capture of cadaveric fingerprints. Both are single-operator units that, if ridge detail is preserved, can collect a 10-set of finger pad prints in approximately 45 and 90 s, respectively. We present our observations on the restrictions as to when such devices can be used with cadavers. We do, however, illustrate that the images are of sufficient quality to allow positive identification from finger pad prints of the dead. With the development of mobile, handheld, biometric, PDA-based units for the police, we hypothesize that, under certain circumstances, devices such as these could be used for the accelerated acquisition of fingerprint identification data with the potential for rapid near-patient identification in the future.

Can post-mortem blood be used for DNA profiling after peri-mortem blood transfusion?

The question of whether blood transfusions can affect DNA profiling is still a contentious issue throughout the forensic community. It is hypothesised that donor leucocytes present in the administered blood will be detected upon examination of recipient blood. In order to resolve this issue, a selection of theoretical experiments were carried out to determine how much donor DNA must be present for its detection in blood components. Five casework examples of material collected from individuals after massive transfusion, including a case of whole organ transplantation, were also investigated. The results indicated that filtration processes used during blood production do not allow the passage of enough donor leucocytes for detection using current forensic profiling techniques. No evidence of secondary profile alleles were found in any case, indicating that peri-mortem blood transfusion does not affect DNA profiling.

Cutting crime: the analysis of the "uniqueness" of saw marks on bone.

Witness marks produced on bone by the use of saws have traditionally been examined using stereomicroscopy. The marks are typically found on the kerf wall or floor and give important information about the implement that made them. This paper describes a new approach to the analysis of witness marks left on kerf walls and floors from crimes involving dismemberment. Previously, two types of marks have been identified: deep furrows formed during the pull stroke and fine striations formed on the push stroke. These types of striation allow the class of saw to be identified, but not an individual saw. With the advent of environmental scanning electron microscopy (ESEM), insulating materials can now be examined without the need for conductive coatings to be applied. This allows materials to be examined at higher magnifications than those available with stereomicroscopy. Here we report on a new, third type of striation that is visible at higher magnifications on ESEM images. These striations are formed from the imperfections on the cutting teeth of saws and give real possibilities of uniquely identifying whether or not a particular saw was used to cause the mark. In blind trials conducted on sawing of nylon 6.6, different individual saws could be successfully identified even if different people used the saw. We discuss ways in which these results can be extended to bone and how this may assist in the investigation of the act of dismemberment.

Investigation into the usefulness of DNA profiling of earprints.

DNA profiling of biological trace evidence has been used for many years. The application of this technique specifically to the DNA profiling of earprints has not to date been thoroughly investigated. This report presents the results of 60 earprints collected from three healthy adult volunteers under controlled laboratory conditions. DNA profile analysis revealed that high levels of non-donor alleles are observed when earprints are collected for DNA profiling. The source of these non-donor alleles is investigated and the impact that their presence within the profile may have on the use of this technique is discussed.