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This content is taken from the University of Strathclyde's online course, Introduction to Forensic Science. Join the course to learn more.

Skip to 0 minutes and 5 secondsForensic biology is the area of forensic science that deals with biological materials encountered in criminal cases. The most common materials include blood, semen and saliva. And these can be found in a wide range of cases but are most frequently found in physical and sexual assaults. The role of the forensic biologist is to find, identify, analyse and interpret the significance of body fluids in the light of the particular case. This includes considering the distribution of body fluids. For example, in the form of blood patterns at the crime scene or semen stains on an item of underwear.

Skip to 0 minutes and 48 secondsSuch interpretations can be valuable to a case but are subjective. And the scientist must take considerable care to avoid bias. A crucial aspect of forensic biology is identifying who body fluids could have come from. and the most powerful technique for achieving this is DNA profiling.

Skip to 1 minute and 11 secondsIn not much more than 20 years, the law has moved from considering DNA profiling as usurping the role of the jury, to fully embracing it as a distinctive and positive contribution to the investigation and prosecution of crime. DNA profiling has also set a new standard for forensic evidence, sometimes referred to as the gold standard. This is because it has followed a path from discovery to application which is typical of new scientific developments, in that research evidence has been published, peer reviewed, and challenged in the scientific community. For the most part, DNA evidence is probably the most reliable evidence of any kind to enter the criminal justice system.

Skip to 2 minutes and 0 secondsIronically, many other areas of forensic evidence do not live up to these new standards set by DNA. In this module, we will look at the biological basis of DNA profiling and how DNA is analysed and interpreted. A critical factor in the success of DNA profiling has been the implementation of DNA databases. How DNA databases work from country to country varies considerably. But most retain DNA profiles from convicted criminals and blood and body fluids from unsolved crimes.

Skip to 2 minutes and 40 secondsIn some countries, samples are destroyed when a case is complete. And in others, samples are retained indefinitely.

Skip to 2 minutes and 51 secondsWe would encourage you to research how DNA is retained and can be used in your country and to compare it with others. If this is your first encounter with molecular biology, you will be exposed to a great deal of new terminology and technological processes. You're advised to walk through the material steadily and engage your fellow students, to improve your understanding and to support your learning.

Welcome to Week 3

Forensic biology, the identification and interpretation of body tissues and their stains, has become synonymous with “DNA” in the public eye, and no wonder.

The combination of its ability to identify the source of the material to the reasonable exclusion of any other and to do this on stains so small as to be invisible is almost the stuff of science fiction. Spice that with a dash of database controversy and it becomes a natural for the media!

In reality, forensic biology plays an important role in the investigation of crimes against the person, even without any DNA analysis being involved. The reason is that crimes of violence result in the shedding of body tissues and this in itself can be the source of critical evidence. Was a death accident, suicide or murder? DNA analysis alone will not answer that.

The week therefore begins with a basic review of the biology of the body tissues of interest. The focus is on blood, in keeping with the theme of the case, and other body fluids are only briefly mentioned, but the basic principles of screening, identification, and interpretation are the same. We then discuss the principles and application of Blood Pattern Analysis, before closing with some information about DNA.

The material is going to be quite technical in places but don’t get too worried and stuck on the detail if you are finding it difficult. It’s more important that you understand the main points and we have provided links to external YouTube and other resources to help you. We encourage you to get involved in the discussions and ask questions which will also help clarify your learning.

Warning: Some of content presented in this program may be distressing to individuals, particularly younger learners. Notwithstanding, the material is representative of that encountered by forensic scientists and we have presented it in an objective and professional manner.

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This video is from the free online course:

Introduction to Forensic Science

University of Strathclyde