theories

key idea - Lombroso argued that criminals are physically different from non-criminals, for example in terms of their facial characteristics. 

Strengths 

•  Lombroso was the first person to study crime scientifically, using objective measuremeants to gather evidence. previously crime was seen as a moral or religios issue. 
• His research showed the importance of examining clinical and historical records of criminals. 
• His later work took some limited account of social and environmental factors, not just heredity.
• By arguing that offenders were not freely choosing to commit crime, lombroso helps us to focus on how we might prevent further offending rather then simply punishing offenders. 

Weaknesses

• Research since lombroso has failed to show a link between facial features and criminality.
• Lombroso failed to compare his findings on prisioners with a control group of non- criminals. had he done so, he may of found the same characteristics among the general population, in which case, his explanation would be invalid. 
• By describing criminals as like "primitive savages", Lombroso equates non-western societies with criminals. This is a form of racism. 

Key idea - Sheldon argues that somatype (body type) is related to criminality; mesomorphs are more likely than other types to commit crimes. 

strengths 

• Other studies have replicated sheldons findings. Glueck abd Glueck found that 60% of the offenders in their study were mesomorphs. 
• The most serious deliquents in sheldons sample were the ones with the most extreamly mesomorphic body shapes. 

Weaknesses

• Glueck and Glueck found that criminality was best explained not by biology alone, but by a combination of biological, psychological and environmental factors. 
• Criminals may develop a mesomorphic build as a result of needing to be physically tough t succeed. if so, criminality causes somatype, rather than somatype causing criminality. 
• social class may be the true cause both of offending and of mesomorphy. convicted offenders are mainly working class males, who are more likely to be in manual jobs where they aquire an athletic build.
• Labelling may play a part. mesomorphs may be labelled as trouble makers because they fit the "tough guy" sterotype, resulting in a self- forfilling prophecy. or they may attract more police attention and get caught more then other somatotypes. 
• Sheldon doesnt account for those endomorphs and ectomorphs who do commit crimes. nor does he explain whether mesomorphs commit crimes other than violence. 

key idea- genetic theories argue that crime has genetic causes. identical (MZ) twins are genetically indentical, so if one is criminal, we should find the other is too. 

strengths 

• Because MZ twins are genetically identical, it is logical to examine whether their offending behaviour is also identical. 
• twin studiea give some support to genteic explanations. Ishikawa and Raine foun a higher concordance rate for identical than for non-identical twins. (the concordance rate measures the probability of both twins being criminals, if one of them is)

Weaknesses

• if genes were the only cause of criminality, identical twins would show 100% concordance, but studies only show around half or less.
• Higher concordance rates between identical twins may be due to sharing the same home, school ect. Their shared environment might cause similarities in their criminal behaviour, not identical genes.
• Parents treat identical twins more alike than they do non-identical twins. Also, identical twins may feel closer that non-identical twins do, so one twin may be influenced by the others criminality to become criminal too. these environmental factors may produce simular behaviour. 
• it is impossible to isolate and measure the effect of genes separatly from environmental effects.
• in early studies, there was no way of knowing for certian if twins were in fact genetically identical, since DNA testing did not exist. 

key idea- Comparing adopted childrens level of criminality with that both of their biological parents and their adoptive parents may allow us to see how far genes influence criminality. 

strengths

• Adoption studies overcome the problem faced by twin studies, where biological identical twins are brought up in the same household, which makes it impossible to separate out the influence of genes from environment.
• The research design is logical, in theory it allows us to see the relative importance of "nature" ( the genes inherited from biological parents) versus "nurture" ( the adoptive family environment) 
• Findings of adoption studies give some support to genetic explanations. they show adoptees were more likely to have criminal records if their biological parents had criminal records. 

Weaknesses

• Gottfredson and Hirschi argue that adoption studies show genes have little effect on criminality.
• Adopted children are often placed in environments similar to those in their birth family, with familes of the same class and ethnicity, in the same locality etc. Similar environments may produce similar behaviour. 
• Many children are not adopted immediately after birth but remain with thier biological family for some time. This early environment may be the true cause of their criminality. 

key idea - some males have an extra Y chromosome, which may cause violent behaviour.

strengths 

• Jacob et al found an association between XYY syndrome and offenders imprisoned for violent behaviour.
• Price and Whatmore found some links between the sybdrome and property crime. 

Weaknesses 

• Even if some violent offenders have the syndrome, this doesnt prove it is the cause of their violence.
• XYY males are tall and well built, so they fit the stereotype of "violent offender" and get labbled as such by the courts, so they are more likely to get a prison sentence. As a result, XYY males are over represented in samples drawn from prisioners and this overstates the importance pof the syndrome as a possible cause of crime. 
• Alternatively, XYY males may be over represented in prison because they often have low intelligence, meaning they are more likely to be caught. samples drawn from prisoners are therefore skewed. 
• The syndrome is very rare ( only 1 in 1,000 men have it ) so it cannot explain much crime.

key idea- injuries, disorders and diseases of the brain may cause it to malfunctionin ways that change personality, morals or self-control, leading to criminal behaviour. 

strengths 

• in a few extreme cases, brain injury or disease has led to some major changes in an individuals personality and behaviour including criminality. 
• There is some correlation between abnormal EEG readings (which measures brainwave activity) and psychopathic criminality. 
• Prisoners are more likely than a non- prisoners to have a brain injury.

Weaknesses

• Crimes caused by brain unjury or desease are rare. The suffers original personality is more important in whether they engage in crime. 
• It is not clear that abnormal brainwave activity causes pyschopathic criminality. some psychopaths have normal EEG patterns and some normal people have abnormal EEG patterns.
• Prisoners higher likelyhood of brain injury could be a result of their criminality ( e.g getting into fights ) rather than a cause if it. 

Key idea - Biochemical factors may trigger criminal behaviour by affecting btain chemistry and mental processes.

Strengths 

• sexual hormones, bloody sugar levels and substance abuse can affect mood, judgement and aggression. 
• Testosterone levels and male offending both peak around the same age, suggesting hormones affect criminal behaviour. 
• Alcohol produces disinhabitation, reducing self control and leading to criminal behaviour, particularly violence. crack cocain has been strongly linked to violent crimes. 
• Biochemical factors are recognised by the courts. The law of infanticide states that if a mother kills her baby as a result of post natal depression or breatfeeding, she has a partial deffence to murder. Pre mentsural tension (PMT) has been accepted as a defence in shopliffting cases. 

Weaknesses 

• Biochemical processes may predispose some individuals to offend, but it may require and environmental trigger to cause actual offending. 
• Scarmella and Brown found testostrone levels do not greatly affect agression levels in most men. 
• Schallling found high testosterone levels in young males led to verbal agression, but not physical violence.
• Infanticide may be due to isolation and the responsibility for caring for a newbron child rather than hormones. 

• Environmental factors - Biological theories ignore invonmental factors. A persons biology may give them otentionally criminal characteristics (e.g. aggressiveness) but they may need an environmental trigger to engage in criminal act. 
• Sample bias - Researchers often use studies of convicted criminals, but these may not be representative of the criminals who got away, so they are not a sound basis for generalising about all criminals. 
• Gender bias - Most biological research focuses on males, so it does not expain female criminality. 
• Crime is a social construct - What counts as crime varies between cultures and over time, so it makes no sense to look for universal explanations , as biological theorists do.