Dogs discriminate identical twins

Earlier studies have shown variation among experimental attempts to establish whether human monozygotic twins that are genetically identical also have identical individual scents. In none of the cases were the dogs able to distinguish all the individual scents of monozygotic twins living in the same environment if the scents were presented to them separately. Ten specially trained police German Shepherd dogs of three Czech Republic Police Regional Headquarters were used for scent identification in our study. The dogs were supposed to match scents of two monozygotic pairs (5 and 7 years old) and two dizygotic twin pairs (8 and 13 years old). Scents were collected on cotton squares stored in glass jars. Dog handlers were blind to the experiment details. In each trial (line-up), one scent was used as a starting scent and the dog was then sent to determine if any of the 7 presented glass jars contained a matching scent. Scents of children of similar ages were used as distractors. In the matching procedure, the dogs matched correctly the scent of one twin with the other, as well as two scents collected from every single identical and non-identical twin to prove their efficacy and likewise, the presence of the matching twin scent in any given glass jar. All dogs in all trials distinguished correctly the scents of identical as well as non-identical twins. All dogs similarly matched positively two scents collected from the same individuals. Our findings indicated that specially trained German Shepherd dogs are able to distinguish individual scents of identical twins despite the fact that they live in the same environment, eat the same food and even if the scents are not presented to them simultaneously.     

Effects of subpopulation structure on probability calculations of DNA profiles from forensic PCR analysis

DNA typing for forensic identification is a two-step process. The first step involves determining the profiles of samples collected at the crime scene and comparing them with the profiles obtained from suspects and the victims. In the case of a match that includes the suspect as the potential source of the material collected at the crime scene, the last step in the process is to answer the question, what is the likelihood that someone in addition to the suspect could match the profile of the sample studied? This likelihood is calculated by determining the frequency of the suspect's profile in the relevant population databases. The design of forensic databases and the criteria for comparison has been addressed by the NRC report of 1996 (National Research Council, 1996). However, the fact that geographical proximity, migrational patterns, and even cultural and social practices have effects on subpopulation structure establishes the grounds for further study into its effects on the calculation of probability of occurrence values. The issue becomes more relevant in the case of discrete polymorphic markers that show higher probability of occurrence in the reference populations, where several orders of magnitude difference between the databases may have an impact on the jury. In this study, we calculated G values for all possible pairwise comparisons of allelic frequencies in the different databases from the races or subpopulations examined. In addition, we analyzed a set of 24 unrelated Caucasian, 37 unrelated African-American, and 96 unrelated Sioux/Chippewa individuals for seven polymorphic loci (DQA1, LDLR, GYPA, HBGG, D7S8, GC, and D1S80). All three sets of individuals where sampled from Minnesota. The probability of occurrence for all seven loci were calculated with respect to nine different databases: Caucasian, Arabic, Korean, Sioux/Chippewa, Navajo, Pueblo, African American, Southeastern Hispanic, and Southwestern Hispanic. Analysis of the results demonstrated marked differences in the probabilities of occurrence when individuals were compared to the different populations and subpopulation databases. The possible genetic and forensic consequences of subpopulation structure on probability calculations are discussed.     

Attention to uninformative features expressed by pigeons in a duration matching-to-sample task

Pigeons were trained on a matching-to-sample task in which they had to respond to a different choice stimulus following the same durations (2 or 10 s) of two different signals. The duration signals consisted of a white light presented from the ceiling and a red light presented from the front wall. Subsequent test performance indicated that matching accuracy declined (1) when the set of choice stimuli following a duration signal differed from the set presented during training, and (2) when the color or location of the duration signal was changed from values used during training. These results are discussed in terms of attention to uninformative features of a visual stimulus.     

Fixed-bin analysis for statistical evaluation of continuous distributions of allelic data from VNTR loci, for use in forensic comparisons.

The detection of DNA polymorphisms by RFLP analysis is having a major impact on identity testing in forensic science. At present, this approach is the best effort a forensic scientist can make to exclude an individual who has been falsely associated with an evidentiary sample found at a crime scene. When an analysis fails to exclude a suspect as a potential contributor of an evidentiary sample, a means should be provided to assess suitable weight to the putative match. Most important, the statistical analysis should not place undue weight on a genetic profile derived from an unknown sample that is attributed to an accused individual. The method must allow for limitations in conventional agarose-submarine-gel electrophoresis and Southern blotting procedure, limited sample population data, possible subpopulation differences, and potential sampling error. A conservative statistical method was developed based on arbitrarily defined fixed bins. This approach permits classification of continuous allelic data, provides for a simple and portable data-base system, and is unlikely to underestimate the frequency of occurrence of a set of alleles. This will help ensure that undue weight is not placed on a sample attributed to an accused individual.     

Familial identification: population structure and relationship distinguishability

With the expansion of offender/arrestee DNA profile databases, genetic forensic identification has become commonplace in the United States criminal justice system. Implementation of familial searching has been proposed to extend forensic identification to family members of individuals with profiles in offender/arrestee DNA databases. In familial searching, a partial genetic profile match between a database entrant and a crime scene sample is used to implicate genetic relatives of the database entrant as potential sources of the crime scene sample. In addition to concerns regarding civil liberties, familial searching poses unanswered statistical questions. In this study, we define confidence intervals on estimated likelihood ratios for familial identification. Using these confidence intervals, we consider familial searching in a structured population. We show that relatives and unrelated individuals from population samples with lower gene diversity over the loci considered are less distinguishable. We also consider cases where the most appropriate population sample for individuals considered is unknown. We find that as a less appropriate population sample, and thus allele frequency distribution, is assumed, relatives and unrelated individuals become more difficult to distinguish. In addition, we show that relationship distinguishability increases with the number of markers considered, but decreases for more distant genetic familial relationships. All of these results indicate that caution is warranted in the application of familial searching in structured populations, such as in the United States.     

Detection of Illicit Drugs by Trained Honeybees (Apis mellifera)

Illegal drugs exacerbate global social challenges such as substance addiction, mental health issues and violent crime. Police and customs officials often rely on specially-trained sniffer dogs, which act as sensitive biological detectors to find concealed illegal drugs. However, the dog “alert” is no longer sufficient evidence to allow a search without a warrant or additional probable cause because cannabis has been legalized in two US states and is decriminalized in many others. Retraining dogs to recognize a narrower spectrum of drugs is difficult and training new dogs is time consuming, yet there are no analytical devices with the portability and sensitivity necessary to detect substance-specific chemical signatures. This means there is currently no substitute for sniffer dogs. Here we describe an insect screening procedure showing that the western honeybee (Apis mellifera) can sense volatiles associated with pure samples of heroin and cocaine. We developed a portable electroantennographic device for the on-site measurement of volatile perception by these insects, and found a positive correlation between honeybee antennal responses and the concentration of specific drugs in test samples. Furthermore, we tested the ability of honeybees to learn the scent of heroin and trained them to show a reliable behavioral response in the presence of a highly-diluted scent of pure heroin. Trained honeybees could therefore be used to complement or replace the role of sniffer dogs as part of an automated drug detection system. Insects are highly sensitive to volatile compounds and provide an untapped resource for the development of biosensors. Automated conditioning as presented in this study could be developed as a platform for the practical detection of illicit drugs using insect-based sensors.     

Forensic value of pollen from ornamental indoor plants

Pollen is deposited almost everywhere and can be gathered and analysed. This work is part of a survey dedicated to indoor pollen from a forensic point of view. Ornamental plants were introduced into a private flat. Their influence on the pre-existing pollen assemblages was documented. Results show that ornamental plants can dramatically change the pollen spectra of indoor locations. The severity of this impact strongly varies with different plant taxa. These findings are important for forensic investigations, since such an ‘artificial’ pollen spectrum leaves an unusual trace and could subsequently relate a suspect to a crime scene.     

Likelihood ratios for evaluating DNA evidence when the suspect is found through a database search

A crime has been committed, and a DNA profile of the perpetrator is obtained from the crime scene. A suspect with a matching profile is found. The problem of evaluating this DNA evidence in a forensic context, when the suspect is found through a database search, is analysed through a likelihood approach. The recommendations of the National Research Council of the U.S. are derived in this setting as the proper way of evaluating the evidence when finiteness of the population of possible perpetrators is not taken into account. When a finite population of possible perpetrators may be assumed, it is possible to take account of the sampling process that resulted in the actual database, so one can deal with the problem where a large proportion of the possible perpetrators belongs to the database in question. It is shown that the last approach does not in general result in a greater weight being assigned to the evidence, though it does when a sufficiently large amount of the possible perpetrators are in the database. The value of the likelihood ratio corresponding to the probable cause setting constitutes an upper bound for this weight, and the upper bound is only attained when all but one of the possible perpetrators are in the database.     

Assessment of pollen assemblages on footwear for evidence of pollen deriving from a mock crime scene: a contribution to forensic palynology

To provide evidence of a link between a crime scene and a suspect, pollen analysis is occasionally employed. However, experimental research linking pollen on footwear to a specific crime scene has been infrequently undertaken such that there are limited references to cite in court. In this blind study, the author had to determine, which of 12 pairs of footwear had walked on a mock scene by comparing their assemblages to those of two scene controls. An additional four control pairs of footwear that had not been worn on or near the scene were also analysed. The pollen data from the footwear was assessed and compared with the scene control samples for: number of taxa, key types, Czekanowski Coefficient and general assemblages. Results indicated that six of the pairs of footwear had walked on the scene and these were, indeed, the ones that actually had done so. The four control pairs were dissimilar in most aspects, particularly key types. This research demonstrates, with some limitations, that evidence of a match between footwear sample and location can be found, even when material from other habitats is present on an exhibit.     

Nosewitness Identification: Effects of Negative Emotion

Every individual has a unique body odor (BO), similar to a fingerprint. In forensic research, identification of culprit BOs has been performed by trained dogs, but not by humans. We introduce the concept of nosewitness identification and present the first experimental results on BO memory in witness situations involving violent crimes. Two experiments indicated that BO associated with male characters in authentic videos could later be identified in BO lineup tests well above chance. Moreover, culprit BO in emotional crime videos could be identified considerably better than the BO of a male person in neutral videos. This indicates that nosewitness identification benefits from emotional encoding. Altogether, the study testifies to the virtue of body odor as a cue to identify individuals observed under negative emotion.     

Forensic applications of DNA fingerprinting

In many ways, DNA profiling technology is very similar to the conventional techniques used for forensic identification. As with, for example, blood grouping techniques, the molecular characteristics of the scene of crime sample may be determined and compared with those of the scene of reference samples from suspects and victim. If the molecular characteristics of the crime sample and the suspect are different, then they cannot be from the same person, whereas if they match, then the possibility remains that they may be from a single source. Similar material, such as blood or semen stains, may be used for both biochemical and genetic tests, and the main applications of identification and relationship testing are shared by both techniques. At this point, the similarity ends; DNA profiling has the following characteristics:

1. It is more sensitive, being able to generate sound data from only a tiny amount of even partially degraded biological material.
2. It is capable of resolving mixtures of semen or tissue from up to several individuals.
3. It has a far greater power of discrimination between individuals—sometimes up to 1 millionfold higher than conventional techniques.
4. It provides considerably more information on the nature of relationships, particularly in cases of incest.

As such, the technique represents a quantum leap in forensic identification and relationship testing.     

Rats exhibit asymmetrical retention functions for hedonic samples

Rats were trained in a symbolic delayed matching-to-sample task to discriminate hedonic sample stimuli that consisted of food or no food. Retention functions decreased more rapidly on trials initiated by a food sample than on trials initiated by a no-food sample when retention intervals were manipulated within session. The asymmetrical functions could not be explained in terms of mediation of choice responding by magazine head-entry behavior during the retention interval. Unlike within-session changes in retention interval, between-session changes did not result in steeper forgetting functions for food samples. These results in rats are consistent with previous findings reported for the presence and absence of visual samples in pigeons (Wixted, 1993).     

Potential significance of medicinal plants in forensic analysis: A review

Medicinal plants are a two-edged sword that might be exploited as a treatment specific dosage, and as deadly poisonous substances to commit murder or suicide when administered in high doses. Forensic experts can collect traces and residual materials from these toxic medicinal plants at a crime scene as forensic evidence. Further, more investigations need to be deeply implemented to in the future to understand the significance of medicinal plants in forensic investigations to detect these criminal offenses. Additionally, to provides a deep understanding of chemical substances that can impact human life positively or negatively with different doses as well as identifying the optimal or overdose concentrations for either treatments or poisonous effects using recent biotechnological approaches. This review aims to illustrate different contributions and the significance of medicinal plants in the field and further employment in the context of forensic science, especially in the Kingdom of Saudi Arabia.     

Cross-modal representation of human caretakers in squirrel monkeys

We tested whether squirrel monkeys have cross-modal representations of their human caretakers with a 0-delay symbolic matching-to-sample procedure. We first trained the monkeys to match photographs of two of their caretakers. After reaching criterion, they were exposed to two test sessions. In these sessions 32 all-reinforced test trials were interspersed among the training trials. In the test trials, a voice, either matching (congruent condition) or mismatching (incongruent condition) with the sample photographs, was played back after the sample stimulus disappeared. The monkeys' matching accuracies in the incongruent condition were lower than in the match condition. Post hoc analyses revealed that the presentation of the primary caretaker's voice interfered with performance in test trials where the secondary caretaker's face was presented (incongruent condition). This suggests that our subjects recalled their primary caretaker's representation upon hearing the appropriate voice.     

The Differential Outcomes Effect in Pigeons (Columba livia): Is It Truly Anticipatory?

We used delay-interval interference to investigate the nature of the differential outcomes effect (DOE) in pigeons. Birds were trained on a delayed matching-to-sample (DMS) task under either common outcome or differential outcome conditions, and then presented with visual interference during the delay period. Consistent with previous literature, the common outcomes birds were slower to learn the DMS task than the differential outcomes birds. The common outcome birds were also more impaired by the visual interference than the differential outcomes birds. Our findings are consistent with the view that the birds trained with common outcomes were likely remembering the sample stimulus during the delay period, and hence were disrupted by the visual interference, whereas the birds trained with differential outcomes were likely relying on the different emotional reactions elicited by the different outcomes to guide their choice behaviour, and hence were less affected by the visual interference. Our findings suggest that the DOE is not truly evidence of anticipatory mediation of short-term retention in pigeons, but rather emotionally driven decision making, which is not truly anticipatory in nature.     

Complex memories in honeybees: can there be more than two?

Foraging honeybees are likely to learn visual and chemical cues associated with many different food sources. Here, we explore how many such sources can be memorized and recalled. Marked bees were trained to visit two (or three) sugar feeders, each placed at a different outdoor location and carrying a different scent. We then tested the ability of the bees to recall these locations and fly to them, when the training scents were blown into the hive, and the scents and food at the feeders were removed. When trained on two feeder locations, each associated with a different scent, the bees could correctly recall the location associated with each scent. However, this ability broke down when the number of scents and feeder locations was increased to three. Performance was partially restored when each of the three training feeders was endowed with an additional cue, namely, a distinct colour. Our results suggest that bees can recall a maximum of two locations when each is associated with a different scent. However, this number can be increased if the scent cues are augmented by visual cues. These findings have implications for the ways in which associations are established and laid down in honeybee memory.     

Forensic biology: its past, present and future

Forensic biology has reached an unprecedented prominence with the advent of DNA profiling, which allows the biologist to use microscopic evidence to match a person to a scene of crime. But there's a lot more in the forensic biologist's arsenal. Here we take a brief look at the who, when and how (and a little of the where to) of forensic biology.     

全基因组扩增技术及其在法医个体识别中的应用

全基因组扩增(Whole genome amplification,WGA)技术是一种对全部基因组序列进行非选择性扩增的技术。近几年来,对WGA技术扩增痕量DNA检材的研究日渐深入,这些研究可望用于刑案现场采集到的痕量DNA样品的扩增,为法医个体识别提供足量的DNA模板。然而,对实际案件中复杂检材的扩增偏差问题一直困扰着法医工作者,寻求一个低扩增偏差、高扩增产率的WGA技术是法医工作者的主要目标。文章综述了WGA技术在法医个体识别中的研究进展及应用前景,为法医解决扩增偏差问题提供参考。     

Does training make you smarter? The effects of training on dogs’ performance (Canis familiaris) in a problem solving task

This study investigates the influence of training experiences on dogs’ performance in a problem solving task, namely opening a box to obtain food. One hundred and eighteen dogs allocated to two different groups according to their training experience (no/basic training vs high level training) were tested. In each group the dogs saw the researcher manipulating either the paw-pad or the lid, prior to being allowed free access to the apparatus. No effect of the locus of manipulation was observed. However, there was a strong effect of training on the dogs’ performance regardless of manipulation condition. Compared to untrained dogs, highly trained dogs were more successful in opening the box and spent significantly more time interacting with the apparatus; whereas untrained dogs spent significantly more time looking back at their owners and the researcher.

These results indicate that high levels of training improve dogs’ problem solving ability, with dogs appearing to be more proactive in the their interaction with novel objects.     

DNA methylation: the future of crime scene investigation?

Proper detection and subsequent analysis of biological evidence is crucial for crime scene reconstruction. The number of different criminal acts is increasing rapidly. Therefore, forensic geneticists are constantly on the battlefield, trying hard to find solutions how to solve them. One of the essential defensive lines in the fight against the invasion of crime is relying on DNA methylation. In this review, the role of DNA methylation in body fluid identification and other DNA methylation applications are discussed. Among other applications of DNA methylation, age determination of the donor of biological evidence, analysis of the parent-of-origin specific DNA methylation markers at imprinted loci for parentage testing and personal identification, differentiation between monozygotic twins due to their different DNA methylation patterns, artificial DNA detection and analyses of DNA methylation patterns in the promoter regions of circadian clock genes are the most important ones. Nevertheless, there are still a lot of open chapters in DNA methylation research that need to be closed before its final implementation in routine forensic casework.