Characterisation of forward stutter in the AmpFlSTR® SGM Plus® PCR

PCR amplification of tetrameric short tandem repeats (STRs) can lead to Taq enzyme slippage and artefact products typically one repeat unit less in size than the parent STR. These back stutter or n ? 4 amplification products are low-level relative to the amplification of the parent STR but are widely seen in the forensic community where tetrameric STRs are employed in the generation of DNA profiles. To aid the interpretation of DNA mixtures where minor contributor(s) might be present in comparable amounts to the back stutter products, the typical amounts of back stutter generated have been well characterised and guidelines for interpretation are in place. However, further artefacts thought to be Taq enzyme slippage leading to products with one repeat unit greater than the parent sequence (n + 4 or forward stutter) or two repeats less (n ? 8 or double back stutter) also occur, but these have not been well characterised despite their potential influence in mixture interpretations. Here we present findings with respect to these additional artefacts from a study of 10,000 alleles and include guidelines for interpretation.     

TrueAllele® Genotype Identification on DNA Mixtures Containing up to Five Unknown Contributors

Computer methods have been developed for mathematically interpreting mixed and low‐template DNA. The genotype modeling approach computationally separates out the contributors to a mixture, with uncertainty represented through probability. Comparison of inferred genotypes calculates a likelihood ratio (LR), which measures identification information. This study statistically examined the genotype modeling performance of Cybergenetics TrueAllele^® computer system. High‐ and low‐template DNA mixtures of known randomized composition containing 2, 3, 4, and 5 contributors were tested. Sensitivity, specificity, and reproducibility were established through LR quantification in each of these eight groups. Covariance analysis found LR behavior to be relatively invariant to DNA amount or contributor number. Analysis of variance found that consistent solutions were produced, once a sufficient number of contributors were considered. This study demonstrates the reliability of TrueAllele interpretation on complex DNA mixtures of representative casework composition. The results can help predict an information outcome for a DNA mixture analysis.     

Duplex-specific nuclease (DSN): A method for the rehabilitation of low-copy number DNA profiles

A continual challenge in the field of forensic DNA analysis is the amplification and interpretation of degraded and low-copy number (LCN) DNA obtained from amounts of limited biological evidence. It has been well established that DNA profiles obtained from the amplification of low quality, degraded, and/or LCN DNA samples are often of limited value due to the frequent occurrence of preferential amplification during polymerase chain reaction (PCR). The by-products of preferential PCR amplification are often observed as inter- and intra-locus peak imbalance, allelic dropout, and/or locus dropout. These are all artifacts that are identified during the interpretation phase of analysis rather than by improving the quality of the DNA present. While it is theoretically possible to obtain a complete DNA profile from a single cell, in reality, profiles obtained from suboptimal amounts of DNA are difficult to interpret and frequently inconsistent when replicated. Inspired by advances in next-generation sequencing techniques, we propose a methodology for simultaneously normalizing the abundance of PCR products across all short tandem repeat (STR) loci using the DNA exonuclease, duplex-specific nuclease (DSN). DSN is an enzyme isolated from the hepatopancreas of Red King (Kamchatka) crab that possesses a strong affinity for digesting double stranded DNA (dsDNA) and has limited activity toward single stranded DNA (ssDNA). Degraded DNA known to display peak imbalance and allele dropout was amplified using AmpFlSTR^® Identifiler^® Plus for 28 cycles. Following amplification, samples were denatured at 99.9 °C for 5 min and incubated with one unit of DSN at 62 °C in a 28 μl volume for 1 min. Nuclease activity was terminated through the addition of equal volume of 10 mM EDTA and 95 °C incubation for 2 min. Following DSN treatment, 21 of 30 alleles within the known profile exhibited some improvement in peak height balance. The findings obtained support the potential use of DSN treatment as a method for normalizing STR profiles and improving the quality of data from degraded and low quantity DNA samples.     

Experimental forensic studies of the preservation of pollen in vehicle fires

The implications of the recent recommendations of the Law Commission regarding the use of admissibility tests have the potential to be far reaching for forensic disciplines that rely on the expertise of highly qualified expert witnesses. These disciplines will need a concomitant body of peer-reviewed experiments that provides a basis for the interpretations of such evidence presented in court. This paper therefore, presents such results from two experiments which were undertaken to address specific issues that were raised in cases presented in the British courtroom. These studies demonstrate that there is a variability in the persistence of Lily, Daffodil and Tulip pollen when exposed to high temperatures between 0.5 min and 1440 min (24 h). It was possible to identify all three pollen types after 30 min of exposure to 400 °C, and after shorter time frames the threshold for successful identification was 700 °C after 0.5 min for all pollen types tested and 500 °C for Daffodil and Lily after 5 min of heat exposure. Over longer time periods (18 h (1080 min)) the different pollen types were found to persist in a viable form for identification at 300 °C (Lily), 200 °C (Daffodil) and 50 °C (Tulip). These findings, albeit from a small sample of pollen types, provide empirical contextual information that would contribute to such evidence having sufficient scientific weight to meet admissibility criteria and be viable evidence for a court. These studies demonstrate the value in seeking pollen evidence from even such extreme crime scenes as encountered in vehicular fires.     

Pressing need for national governmental recognition of forensic anthropology in South Africa as illustrated in a medico-legal case

Forensic anthropology in South Africa is well developed in the higher education sector, with advanced training and research programmes. Despite this and decades of academic involvement in casework, forensic anthropology still lacks a defined framework and mandate at a governmental level. Therefore, the involvement of forensic anthropologists’ expertise varies markedly between cases, provinces, and among various stakeholders within the country, to the detriment of dispensation of social and criminal justice. The lack of clearly defined guidelines for the rendering of the service was exemplified and demonstrated through a recent forensic case. Here, contextual information was absent, and the remains posed a challenge to analyse, ostensibly due to missing information. Numerous questions were raised during the analysis of the remains, and broader concerns about the investigative involvement of a forensic anthropologist within South African casework were brought to the fore. Through the analysis of this case, we describe the deductive processes that led to the formation of an opinion that the skeletal linear defects were the result of taphonomic changes. In addition, we highlight how these efforts where constrained and each step in the process unnecessarily hindered. Finally, we demonstrate the capacity and willingness of forensic anthropology practitioners to be involved, and how, without governmental support, it is a great potential lamentably untapped.     

Development and validation of highly selective screening and confirmatory methods for the qualitative forensic analysis of organic explosive compounds with high performance liquid chromatography coupled with (photodiode array and) LTQ ion trap/Orbitrap mass spectrometric detections (HPLC-(PDA)-LTQOrbitrap)

An LTQ-Orbitrap FTMS is a new (hybrid) mass spectrometric (MS) analyzer. It allows for the acquisition of full scan MSⁿ (n-stage fragmentations, n = 1 − n) spectra with the linear ion trap detector (LTQ) at high speed and/or with the Fourier Transform-detector (Orbitrap) with ultra high mass resolution (> 60,000 at m/z < 400 amu) and high mass accuracy (≤ 1 ppm with internal calibration). In addition it may be coupled with liquid chromatography (LC) with photo diode array (PDA) detection.Two methods for the forensic screening and confirmation of all common trace explosives in post-blast residues have been developed on this instrument using atmospheric pressure chemical ionization (APCI). In one run, the nitrogen-containing explosives are analyzed with the combination of “LC-(PDA)-APCI(−)-LTQ MS²/Orbitrap FTMS” (Method 1). In another run, peroxide explosives are analyzed with “LC-APCI(+)-LTQ MS²/Orbitrap FTMS” (Method 2).The performance of both methods has been validated according to procedures defined in the EU COMMISSION DECISION implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results (DC 2002/657/EC) and other standards (NEN 17025 and NEN 7777). The methods are highly selective due to the simultaneous utilization of the Orbitrap FTMS and LTQ MS², both of which are highly selective detectors Tested explosive compounds can be detected in the molecular ion form by the Orbitrap analyzer with minimal mass interference in different matrices when using an extremely narrow mass tolerance detection window (≤ 2 ppm). The identification of a detected compound follows an identification point system. Experimental results show that almost all explosive compounds meet the confirmation criteria (minimum 4 points) required for the positive identification by the DC 2002/657/EC.     

Distribution of 6-monoacetylmorphine and morphine in head and pubic hair from heroin-related deaths

There is limited published data to aid interpretation of analytical findings from hair analysis. The aim of the study was to collate 6-monoacetylmorphine (6-AM) and morphine concentrations in head and pubic hair from heroin users and to propose reference ranges and relate these to the amount of heroin used. The ratio of morphine-to-6-AM was also investigated. A total of 82 head hair samples divided into 173 segments of various lengths and 15 pubic hair samples were collected at postmortem from heroin users. The hair was analysed using a previously published method. A statistical evaluation demonstrated that in head hair, the lower, middle and upper concentration ranges of 6-AM were 0.1–0.9, 0.9–12.5 and 12.5–154.1 ng/mg and those of morphine were 0.1–0.8, 0.8–6.0 and 6.0–36.3 ng/mg. In pubic hair, the lower, middle and upper concentration ranges of 6-AM were 0.2–0.5, 0.5–2.3 and 2.3–18.2 ng/mg and those of morphine were 0.2–0.4, 0.4–2.4 and 2.4–13.3 ng/mg. The morphine-to-6-AM ratio showed a large variation. The ratio tended to decrease from proximal to distal segments. The statistical results suggest low, middle and high concentration ranges which we propose can be used for estimating the amount of heroin consumed into corresponding low or occasional, regular or habitual and heavy or excessive drug use. The ratio of morphine-to-6-AM showed great variation and did not support the proposal that a ratio less than 0.77 is needed to prove ingestion of heroin.     

Evaluation of the composition of street cocaine seized in two regions of Brazil

This work evaluates cocaine purity and the concentration ranges of adulterants and inorganic constituents for 31 street cocaine samples seized in two different regions of Brazil from July 2008 to May 2010. Cocaine and adulterants, such as caffeine, lidocaine and benzocaine, were quantified by Gas chromatography–mass spectrometry (GC–MS), and the inorganic constituents were determined by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and ion chromatography (IC). The cocaine concentrations in the samples seized in the Amazonas state (AM samples) ranged from 154 to 978 mg g^? 1, and these samples did not contain any of the adulterants studied. The cocaine concentrations in the samples seized in the Minas Gerais state (MG samples) ranged from 63.9 to 753 mg g^? 1. Caffeine was the main adulterant found in 76% of the MG samples, ranging in concentration from 5.5 to 645.3 mg g^? 1. Lidocaine was found in 66.7% of the MG samples, with concentrations ranging from 16.3 to 576.7 mg g^? 1. Benzocaine was found in only one MG sample, at a concentration of 84.8 mg g^? 1. Fourteen elements were identified by ICP-OES, and a wide variation was observed in the concentrations of Ca, Mg, Na, P, Al, Fe, Mn and Zn. Pearson Product–moment Correlations between the analytes allowed the constituents to be associated with the chemicals used in the manufacturing of cocaine and with some common diluents. The study of the purity of cocaine and the presence and concentration of adulterants and inorganic constituents is important because the latter can have deleterious effects on health.     

The age estimation of blood stains up to 30 days old using visible wavelength hyperspectral image analysis and linear discriminant analysis

A novel application of visible wavelength hyperspectral image analysis has been applied to determine the age of blood stains up to 30 days old. Reflectance spectra from selected locations within the hyperspectral image, obtained from a portable instrument, were subjected to spectral pre-processing. This was followed by the application of a linear discriminant classification model, making estimations possible with an average error of ± 0.27 days for the first 7 days and an overall average error of ± 1.17 days up to 30 days. This is also the first reported study of the determination of the age of fresh blood stains (less than one day old) with an error of ± 0.09 h. The studies have been made under controlled conditions and represent, at this stage, proof of concept results but also are the most accurate age estimation results for measurements between 0 and 30 days reported to date. The results are consistent with well-established kinetic processes suggesting that the pre-processing stages described are revealing spectroscopic changes which are reliably following the time dependent oxidation of HbO₂. The potential for parameterisation of environmental factors to make the method generally applicable at crime scenes is discussed, along with the developments required to further improve classification and to make the instrument genuinely portable.     

Recovery of human DNA profiles from poached deer remains part 2: Improved recovery protocol without the need for LCN analysis

Although poaching is a common wildlife crime, the high and prohibitive cost of specialised animal testing means that many cases are left un-investigated. We previously described a novel approach to wildlife crime investigation that looked at the identification of human DNA on poached animal remains (Tobe, Govan and Welch, 2011). Human DNA was successfully isolated and amplified from simulated poaching incidents, however a low template protocol was required which made this method unsuitable for use in many laboratories. We now report on an optimised recovery and amplification protocol which removes the need for low template analysis.Samples from 10 deer (40 samples total — one from each leg) analysed in the original study were re-analysed in the current study with an additional 11 deer samples. Four samples analysed using Chelex did not show any results and a new method was devised whereby the available DNA was concentrated. By combining the DNA extracts from all tapings of the same deer remains followed by concentration, the recovered quantity of human DNA was found to be 29.5 pg ± 43.2 pg, 31 × greater than the previous study. The use of the Investigator Decaplex SE (QIAGEN) STR kit provided better results in the form of more complete profiles than did the AmpF?STR® SGM Plus® kit at 30 cycles (Applied Biosystems). Re-analysis of the samples from the initial study using the new, optimised protocol resulted in an average increase of 18% of recovered alleles. Over 17 samples, 71% of the samples analysed using the optimised protocol showed sufficient amplification for comparison to a reference profile and gave match probabilities ranging from 7.7690 × 10^? 05 to 2.2706 × 10^? 14.The removal of low template analysis means this optimised method provides evidence of high probative value and is suitable for immediate use in forensic laboratories. All methods and techniques used are standard and are compatible with current SOPs. As no high cost non-human DNA analysis is required the overall process is no more expensive than the investigation of other volume crime samples. The technique is suitable for immediate use in poaching incidents.     

Methodological issues in monitoring the use of coercive measures

PurposeIn many European countries, initiatives have emerged to reduce the use of seclusion and restraint in psychiatric institutions. To study the effects of these initiatives at a national and international level, consensus on definitions of coercive measures, assessment methods and calculation procedures of these coercive measures are required. The aim of this article is to identify problems in defining and recording coercive measures. The study contributes to the development of consistent comparable measurements definitions and provides recommendations for meaningful data-analyses illustrating the relevance of the proposed framework.MethodsRelevant literature was reviewed to identify various definitions and calculation modalities used to measure coercive measures in psychiatric inpatient care. Figures on the coercive measures and epidemiological ratios were calculated in a standardized way. To illustrate how research in clinical practice on coercive measures can be conducted, data from a large multicenter study on seclusion patterns in the Netherlands were used.ResultsTwelve Dutch mental health institutes serving a population of 6.57 million inhabitants provided their comprehensive coercion measure data sets. In total 37 hospitals and 227 wards containing 6812 beds were included in the study. Overall seclusion and restraint data in a sample of 31,594 admissions in 20,934 patients were analyzed. Considerable variation in ward and patient characteristics was identified in this study. The chance to be exposed to seclusion per capita inhabitants of the institute's catchment areas varied between 0.31 and 1.6 per 100.000. Between mental health institutions, the duration in seclusion hours per 1000 inpatient hours varied from less than 1 up to 18 h. The number of seclusion incidents per 1000 admissions varied between 79 up to 745. The mean duration of seclusion incidents of nearly 184 h may be seen as high in an international perspective.ConclusionCoercive measures can be reliably assessed in a standardized and comparable way under the condition of using clear joint definitions. Methodological consensus between researchers and mental health professionals on these definitions is necessary to allow comparisons of seclusion and restraint rates. The study contributes to the development of international standards on gathering coercion related data and the consistent calculation of relevant outcome parameters.     

Choice of population database for forensic DNA profile analysis

When evaluating the weight of evidence (WoE) for an individual to be a contributor to a DNA sample, an allele frequency database is required. The allele frequencies are needed to inform about genotype probabilities for unknown contributors of DNA to the sample. Typically databases are available from several populations, and a common practice is to evaluate the WoE using each available database for each unknown contributor. Often the most conservative WoE (most favourable to the defence) is the one reported to the court. However the number of human populations that could be considered is essentially unlimited and the number of contributors to a sample can be large, making it impractical to perform every possible WoE calculation, particularly for complex crime scene profiles. We propose instead the use of only the database that best matches the ancestry of the queried contributor, together with a substantial F_ST adjustment. To investigate the degree of conservativeness of this approach, we performed extensive simulations of one- and two-contributor crime scene profiles, in the latter case with, and without, the profile of the second contributor available for the analysis. The genotypes were simulated using five population databases, which were also available for the analysis, and evaluations of WoE using our heuristic rule were compared with several alternative calculations using different databases. Using F_ST = 0.03, we found that our heuristic gave WoE more favourable to the defence than alternative calculations in well over 99% of the comparisons we considered; on average the difference in WoE was just under 0.2 bans (orders of magnitude) per locus. The degree of conservativeness of the heuristic rule can be adjusted through the F_ST value. We propose the use of this heuristic for DNA profile WoE calculations, due to its ease of implementation, and efficient use of the evidence while allowing a flexible degree of conservativeness.     

Longevity of spermatozoa in the post-ejaculatory urine of fertile men

Many scientists of varying clinical backgrounds have described the phenomenon of spermaturia in animals, adolescents as well as fertile and infertile men. Nevertheless, research for an expert opinion on a law case in the field of forensic medicine revealed a lack of valid information about the longevity of spermatozoa in post-ejaculatory urine (PEU) of fertile men.Our goal was to measure the appearance of vivid sperm in PEU while considering the factor of time in order to predict a realistic interval, in which positive sperm findings might occur. Therefore ten healthy, young men donated their sperm for fertility analysis and a urine sample prior to and after ejaculation. The time intervals between ejaculation and the first micturition were preset ranging between 30 min and maximal 11 h. Each ejaculate underwent a semen analysis. The pre- and post-ejaculatory urine samples were screened for the presence of viable and motile spermatozoa. Semen parameters were determined and related to the sperm findings in the precipitate of the urine samples. The amount, the viability and motility status of the detected spermatozoa were recorded after each preset time interval.The results showed that none of the 10 participants had sperm in their urine samples prior to ejaculation. The average sperm concentration was 50.1 ± 25.8 million/ml. After a time span of 30 min 59.5% of the first fractions of PEU samples were sperm positive, after 2 and 4 h still 70%, and after 5 h sperm were no longer detected. The last motile spermatozoa could be found after 4.5 h. It seems that remaining sperm in the urethra are washed out with the first micturition in the majority of fertile men, however, the conclusion as to whether sperm findings >5 h after ejaculation are improbable needs to be confirmed by further investigations.     

Age estimation by pulp/tooth area ratio in canines: Cameriere's method assessed in an Indian sample using radiovisiography

Age estimation of an individual whether living or dead is an intimidating task in forensic investigations. Since teeth are more resistant to most peri- and post-mortem changes, they are frequently used for identification and age estimation when skeletal remains are in poor condition. However, most methods are destructive and warrant extraction of teeth which is not feasible in living individuals. Cameriere's et al. put forth a radiographic method of age estimation by pulp to tooth area ratio (AR) in canines and revealed a linear regression between age and the AR. In the present study, we estimated the AR in 456 canines (upper, lower and both) in an Indian sample (114 males and 114 females) using radiovisiography technique. Linear regression equations were derived for upper canine, lower canine and both using the AR to estimate chronological age. Additionally, the efficacy of these equations was also evaluated in younger age group (<45 years). The formulas derived, i.e., age = 96.795 ? 513.561x₁ (Eq. (1)) for upper canine, age = 88.308 ? 458.137x₂ (Eq. (2)) for lower canine and age = 99.190 ? 283.537x₁ ? 306.902x₂ + 400.873x₁x₂ (Eq. (3)) for both the canines were applied to predict the chronological age. The mean value of residuals using these regression equations ranged from 4.28 to 6.39 years with upper canine equation generally giving a precise result. When these equations were applied for younger ages (<45 years), the regression equation derived from both canines gave a better result (mean residual 2.70 years). Overall these equations were better able to predict the age in younger ages, i.e., up to 45 years.     

Forensic oral imaging quality of hand-held dental X-ray devices: Comparison of two image receptors and two devices

Recently, different portable hand-held and battery-powered dental X-ray units have become available. Especially for forensic odontological purposes, they offer diverse advantages such as for use in disaster areas and crime-scene locations as also in autopsy rooms and mortuaries. For any application, the most important feature of these hand-held devices is the delivered image quality. The aim of this study is to evaluate the radiographic image quality acquired by two portable X-ray devices in combination with two types of image receptors and to compare the findings with the image quality of a standard intra-oral X-ray device.Eleven samples consisting of eight teeth, two dry skeletal specimens and one formalin-fixed mandible part were mounted on blocks for standardised (re)positioning. Radiological images were acquired with two hand-held (AnyRay^® 60 kVp, 0.02–4.00 mAs and NOMAD^® 60 kVp, 0.023–2.277 mAs) and one wall-mounted (MinRay^® 60/70 kVp 0.14–22.4 mAs) X-ray device combined with two image receptor systems (VistaScan^® phosphor storage plate (PSP) and SIGMA^® M CMOS Active Pixel technology sensor). The effect of X-ray source-to-object distance (SOD) was checked at 20 cm in conjunction with object to image receptor distances (OIDs) of 0.8 and 2.5 cm. For each parameter setup, the exposure times were run from low till high. An expert consent statement was achieved by agreement of four expert observers selecting the optimal images based on a developed four point quality rating system. Next, a selection of the images was assembled in a set of 198 observation screens and scored by seven observers. The observation screens were designed to compare observer scores, relations between devices, receptors and OIDs and images obtained from the different devices at equal exposure levels (mAs). All results were statistically analysed.Radiological image quality was significantly higher for phosphor plate compared with the CMOS digital receptor system (p < 0.0001). Furthermore, a significantly superior image quality was obtained for OID = 0.8 than for OID = 2.5 (p = 0.039). A significant difference in image quality between the three devices was also established (p = 0.02). The present study demonstrated the feasibility of portable X-ray systems for forensic odontological applications based on rendering optimal image quality, provided an in vitro guideline of optimal parameter settings and offered a radiological image database usable in further research.     

Transfer of fibres on the hands of living subjects and their persistence during hand washing

Textile fibres were transferred to the hands of ten living subjects and their persistence was determined after hand washing. Average number of fibres transferred was 300 ± 133 (female 288 ± 92, male 311 ± 163) per 100 cm² hand area in the 100 experiments. However the number of fibres transferred was not gender dependent but individual dependent. The hand texture of subjects was compared with the number of fibres transferred but the relationship was not observed. The number of fibres transferred varied significantly for the 10 repeated experiments performed under the same conditions for the same subject.The subjects were then asked to wash their hands with water. One test group washed their hands with standing water, and the other with running tap water. Afterwards, the number of fibres remaining on the test subjects' hands were investigated. Migration of the fibres on the surface of the observed hands did occur but total loss of transferred fibre after hand washing did not occur. The average number of fibres remaining per 100 cm² hand area was 14 ± 10 (range = 3–72) for hand washing with standing water, and 10 ± 12 (range = 0–79) for washing with running tap water. The results of this study show the possibility of finding fibres on the hands of a person involved in a criminal case even after hand washing before fibre collection.     

Likelihood ratios for complex mixtures with relatives

Likelihood ratios used for the analysis of complex DNA mixtures depend on a number of modeling assumptions and parameter estimates. In particular, the LR does not give information about the relative weight of the separate contributors for hypotheses conditioned on several contributors. An alternative is to evaluate the observed LR with respect to likelihood ratios expected under the defense hypothesis. Further, a p-value corresponding to the LR can be calculated. The p-value is the probability of observing a LR equally large or larger than the one observed, if the defense hypothesis is true. In this paper we investigate the distribution of likelihood ratios for mixtures with drop-in and drop-out and related contributors. Disregarding a plausible close relative of the suspect as an alternative contributor may overestimate the LR against a suspect.     

Relationship between blood and urine alcohol concentrations in apprehended drivers who claimed consumption of alcohol after driving with and without supporting evidence

For various reasons, many people suspected of driving under the influence of alcohol (DUIA) are not apprehended sitting behind the wheel, but some time after the driving. This gives them the opportunity to claim they drank alcohol after the time of driving or after they were involved in a road-traffic crash. Alleged post-offence drinking is not easy for the prosecution to disprove, which often means that the DUIA charge is dropped or the person is acquitted if the case goes to trial. The routine practice of sampling and measuring the concentration of alcohol in blood (BAC) and urine (UAC) and calculating urine/blood ratios (UAC/BAC) and the changes in UAC between two successive voids furnishes useful information to support or challenge alleged drinking after driving. We present here a retrospective case series of DUIA offenders (N = 40) in half of which there was supporting evidence of an after-drink (eye witness or police reports) and in the other half no such evidence existed apart from the suspect's admission. When there was supporting evidence of an after-drink, the UAC/BAC ratio for the first void was close to or less than unity (mean 1.04, median 1.08, range 0.54–1.21) and the UAC increased by 0.21 g/L (range 0.02–0.57) between the two voids. Without any supporting evidence of post-offence drinking the mean UAC/BAC ratio was 1.46 (range 1.35–1.93) for the first void, verifying that absorption and distribution of alcohol in all body fluids and tissues was complete. In these cases, the UAC between successive voids decreased by 0.25 g/L on average (range 0.10–0.49), indicating the post-absorptive phase of the BAC curve. Long experience from investigating claims of post-offence drinking leads us to conclude that in the vast majority of cases this lacks any substance and is simply a last resort by DUIA offenders to evade justice. Unless supporting evidence exists (eye witness, police reports, etc.) of post-offence drinking the courts are encouraged to ignore this defence argument.