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Case Studies
Prior to the growth of knowledge of Capgras and modern investigative techniques case studies were common place and fuelled this growth in knowledge. Capgras and Reboul-Lachaux's syndrome defining study is one such example and brought the syndrome into the scientific communities awareness. See the above and below sections for more discussion on these examples.

GSR
Galvanic skin response (GSR) has been measured in patients with Capgras delusions. GSR measures the conductance of the skin using electrodes (often on the hands) and can be linked with psychological events. Ramachandran states that when a healthy person is shown pictures of family members, the rate of sweating increases resulting in a change in the GSR, linking the measure to "emotional arousal". However when images of family members were shown to a Capgras sufferer, no GSR change was measured, suggesting a lack of emotional arousal. This lack of emotion was contrary to the fact that the patient acknowledged that those in the image shared a physical resemblance to the real family member. The authors demonstrated the patients GSR did however change when they were exposed to other emotional stimuli concluding the deficit not to be caused by damage to the emotion centres of the brain (E.G. the Amygdala). It is worth noting the pattern of GSR changes demonstrated by capgras patients is different to that of sufferers of a similar syndrome. Prosopagnosia patients show GSR changes but are unable to acknowledge physical similarities resulting in a failure to recognise those they know. Therefore while prosopagnosia appears to occur due to defective overt recognition, literature suggests it is covert recognition that is affected in capgras patients.

Brain Imaging
Magnetic resonance imaging (MRI) and Computerised tomography (CT) have been utilised to gain an understanding in structural brain changes that may lead to behaviours expressed by Capgras patients. However these studies are limited in number and are somewhat limited regarding the findings due to the fact that patients scanned often also have other conditions that may have associated structural changes. This presents challenges to identification of links between structural and behavioural changes.

CT
CT scans have revealed mixed and sometimes opposing. Todd, Dewhurst and Wallis (1981), using CT, found general atrophy of the sulci of the frontal lobes of a capgras sufferer. However the patient presented other conditions that have been associated with cortical atrophy such as parkinsonism and schizophrenia. A study by Forstl, Almeida, Owen, Burns and Howard (1991) of multiple CT scans of Capgras patients revealed 58% had cortical atrophy, however many of these also presented symptoms of other conditions. CT has also been employed to highlight areas affected by traumatic brain injuries that have resulted in capgras delusions. Alexander, Stuss and Benson (1979) found right temporal and bilateral frontal damage may have caused their patients new delusions. However the patient presented different behaviours to those in the Capgras literature such as being apathetic toward the imposter rather than feeling animosity toward them. A further CT study concluded that there were no signs of structural abnormalities of the brain of a Capgras sufferer suggesting the cause could be at the molecular level.

MRI
One of the earliest MRI scans of a patient suffering from Capgras delusions revealed similar areas of damage to those presented in CT scans. However =-this patient had lesions rather than atrophy located bilaterally in the frontal lobe and larger lesions bilaterally to the occipital lobe extending anteriorly into the parietal lobe. This area is commonly associated with spatial visual processing and not recognition tasks.

EEG
Electroencephalography measures the brains activity by placing electrodes on the scalp. A study of 59 patients with misidentification syndromes exclusively involving others revealed 53% as having slow background activity, this has been specifically located in the Occipitotemporal region , an area proposed to be involved in the recognition of multiple stimuli categories such as faces and objects

Meta-Analysis
Articles have combined findings from multiple papers and case histories in order to form a picture of co-morbidity. Meta-analysis have reported capgras to have high concordance rates with other delusional disorders. One such paper reviewed reports that out of 131 instances of Capgras or Fregoli syndrome (another misidentification syndrome), most of which were capgras cases, 52% were also diagnised with schizophrenia and 65% had paranoid psychotic symptoms. Authors have also used meta-anlysis to group data using the above techniques together acquiring a more generalized view of tissue damage and abnormal brain activity that may result in or be a result of Capgras. The technique has also been used in order to compare and contrast Capgras with other misidentification syndromes aiming to develop our understanding of the visual system.

Capgras and Crime
There have been a number of criminal cases committed by suffers of Capgras syndrome, those that most catch the media attention are often homicides. One of the most recent examples of Capgras delusions being used as a defence to murder occurred in 2009 when a male sufferer killed his wife whom he believed to be an imposter. However, in this case the jury did not accept the defence due to concerns that the act seemed too planned out to have only been due to a delusional episode. Other criminal cases reveal Capgras sufferers do not only have delusions in which another person is the impostar. Another murder defendant claimed his Capgras delusions lead him to believe others to have been replaced by aliens, clones and robots. The defendant believed his step-father to have been replaced by a “malevolent robot” clone leading him to kill the impostar robot and open him up in order to find proof. Previously the defendant had threatened to kill his wife and on another occasion had threatened members of the public in a bar believing they were all clones dent by aliens to destroy humans.

The above cases illustrate the threat that can be posed to the general public as well as those emotionally connected to those suffering Capgras delusions. They also highlight the fact that imposters are not always believed to be human and therefore mental illness associated with these delusions appears to cross into schizophrenia type delusions. In many criminal cases the defendant has not only been diagnosed as suffering Capgras delusions but also meet the criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders for Schizophrenia or bi-polar disorder. This suggests that Capgras delusions alone may not result in violence while the presence of other disorders along with Capgras may increase the likelihood of the sufferer to act out violently. However whether this is true is not currently answered by the literature on Capgras. Such cases have however helped fuel the debate as to whether Capgras is merely an element of schizophrenia or can arise independently.