Posts Tagged ‘Science’
Wednesday, December 30th, 2009
What do forensic anthropologists do? They study human bones to determine a biological profile and to assess potential trauma and pathology. What does that mean? It means forensic anthropologists use bones to try to understand what a given person looked like and if they suffered any trauma when they died.
So what can a forensic anthropologist tell from bones? Bones can tell age, sex, stature, bone pathology, nutrition, and sometimes repetitive activities the person had engaged in. Repetitive activity can change the morphology of a skeleton and bones; repetitive, heavy use of certain muscles can affect the size and density of the bones to which they are attached. Poor nutrition also shows up in bones. Rickets, a disease caused by vitamin D and calcium deficiencies, causes bones to become soft, fractured, and deformed.
The age of the person the bones belonged to can be determined relatively accurately using bone fusions and teeth up to the age of 21, after the age of 21 exact age is all but impossible to determine from bones, except for relative old age. Sex can be determined from close examination of the pelvis, which has gone through evolutionary differentiation between men and women, and the skull. Small shape and size differences in these bones can help determine the sex of the skeleton. Race can also be determined, somewhat. Race can be narrowed down to black, white, or Asian using the features of the skull and sometimes the shape of certain teeth. This is becoming more difficult in an age where different races interbreed freely and skull morphology of mixed races is not telling of any one race.
Forensic anthropology also concentrates on potential causes of death, although forensic anthropologists lack the legal authority to declare any official cause of death their opinions are taken into consideration by the medical examiner or coroner. The potential cause of death can sometimes be determined if there are obvious perimortem fractures to the skeleton or gunshot holes or blade cut marks in the bone.
Read about more aspects of forensic sciences
Wednesday, December 9th, 2009
That a person can have more than one DNA profile?
There are people who are human chimeras, who are people who are made up of two different sets of cells with DNA that are only as similar as that of two non-twin siblings. This means that a person can have cheek cells that have different DNA than their skin cells. How does this happen? In a very few instances where there are two fertilized eggs in the womb (fraternal twins) the fertilized eggs fuse together, well before the embryonic stem cells of that egg have begun to differentiate into anything, and become one developing fertilized egg. These eggs carry two different sets of DNA and so the resultant embryo, which will develop into a person, will always have two sets of DNA within it, each set differentiating into some different part of the body. The forensic implications of this are that a person whose DNA is being tested from a cheek swab may not match the skin cell DNA that he/she left behind at a crime scene.
Human chimeras are thought to be very rare, blood chimeras are more common. Blood chimeras are fraternal twins who shared some portion of placenta in the womb. The sharing of placenta caused blood and blood-forming tissue to be exchanged between the twins and to embed in the bone marrow. This causes the twins to have DNA from each other in their blood, which is produced in the bone marrow. The blood of chimeric fraternal twins has two distinct sets of genes and possibly two different blood types.
Read all of our entries on DNA here
Thursday, November 12th, 2009
What is art forgery? For the most part art forgery is the creating and or selling of works of art that are falsely attributed to an artist that did not create the piece of art. This can involve replicating an existing or know piece of art and passing it off as the original or creating a new work of art in the style of another artist and claiming it as a new discovery of a piece discovered from that artist. Art forgery dates back thousands of years, in fact the Romans were know to copy Greek sculptures and sell them as authentic Greek art work over 2,000 years ago.
The driving force of art forgery is the fact that art work created by certain artists is worth more than art work created by others. If a work of art can be replicated perfectly by an art forger it is only worth less monetarily than the original because of who painted it not because the painting looks any differently than the original. The same theory applies to forgers who create new art pieces in the style of a master, if the forgery is believed to be genuine it will be deemed priceless but if it is found to be a fake it is deemed worthless, regardless of what the piece of art looks like.
Forensic investigators, along with art historians and appraisers, are often responsible for determining if a piece of art is a forgery or not. Historians often use stylistic analysis to determine if a work of art is genuine or not, possessing large amount of knowledge about the styles, tool, brushstrokes, techniques used by certain artists. There are a variety of methods used for forensic authentication of art work. Some of the technical methods for revealing fakes include X-rays, UV lights, and IR light, which can be used to see under layers of paint to see covered up works, determine time period or the actual artist of the painting if an original signature has been covered up. Chemical analysis and spectral comparisons can detect the components of paint to ensure that modern pigments were not used in supposedly old paintings. Examination of the craquelure, the network of cracks that appear on old paintings, can be analyzed to ensure that the cracks were not artificially made and that they follow the grain of the wood onto which they were painted.
Art forgery sounds like a thing of the past, but art dealers claim that about 15% of art sold at auctions are fake, which means hundreds of people getting conned out of thousands of dollars.
For more information on art crimes save the date, the Museum’s new art crimes temoporary exhibit is coming on February 15th, 2010!
Learn about ink analysis and other forensic techniques!
Monday, October 12th, 2009
Although one strand of hair cannot be positively matched to a person, hair is still a valuable source of evidence. Because hair can be grouped into three different racial groups it can be used to identify if it came from someone of European, Asian, or African ancestry. As such, hair can be used to exclude people of certain racial group as suspects or as having been at a crime scene.
Hair can yield DNA evidence, if hair is pulled out by the root, as in some violent struggles, it will contain root pulp which is a good source of nuclear DNA (nDNA), the type of DNA most often used in forensics. The hair shaft does not contain nDNA, so the 100-150 strands of hair most people lose daily will not contain a root or nDNA, but it does have mitochondrial DNA (mDNA). MDNA, which cannot be used for individualization, can narrow the source of the hair down to a certain family group (mDNA is passed from mother to all offspring).
Hair can also be used to run drug tests, but these tests are only presumptive and have to be confirmed by blood or urine tests. Hair absorbs chemicals, such as marijuana smoke and arsenic, from the environment and once the chemical is in the hair there is no way of telling if it got there from consumption or from exposure from the environment.
Age cannot be determined from hair, generally the only age determination that can be made from hair is if came from an infant or from an elderly person. The sex of the person the hair came from can also not be determined via hair examination unless there is nDNA evidence such as the root.
Learn more about techniques forensic scientists use
Friday, October 2nd, 2009
Cadaver dogs are the tool most frequently used to find buried dead bodies, as in mass casualty incidents such as earthquakes or bombings as well as single death incidents. But a new tool is now being developed that may be the first step to finding decomposing bodies and determining the time of death electronically. The technology uses the different gases released by a decomposing body for both locating and time of death determination. The human body releases over 30 different compounds at different time intervals as it decomposes, this new technology is working on detailing the time sequence of these compounds as they are released hours and days after death. In order for this technology to be useful scientists have to identify what gases are released in what order under a large number of different environmental factors because environmental factors can affect rate and stages of decomposition. Although cadaver dogs are the gold standard for cadaver detection, their training takes a lot of time and manpower, an electronic device that could do the jobs as well plus determine time of death would be a great new forensic tool.
for more see this Science Daily article
Read more about cadaver dogs and research on body decomposition here