PowerPoint Slideshow about 'DNA evidence' - devaki
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At one time, blood at a crime scene was significant to investigators for its presence alone — bloodstains and spatters often tell their own story of events. But today scientists can perform further tests, including blood typing and DNA analysis, that can help identify the victim or offender. Pictured here is a color-enhanced image of blood cells and platelets, magnified over 5,200 times by a scanning electron microscope.
Investigators can extract DNA from saliva left behind on items — such as cigarettes, envelopes or drinking straws — at the crime scene to help identify their killer or victim. One suspect was connected to the World Trade Center bombing, for example, after authorities matched his DNA with that from saliva on an envelope delivered by one of the conspirators. This saliva has been magnified 40 times.Saliva
In cases of rape and other sexual crimes, the seminal fluid left by the attacker can provide important evidence. Since sperm remains alive for only a short period of time, its condition can indicate the time of the attack; such samples can also provide information on blood type and now identity, through DNA. Pictured here is a color-enhanced image of sperm, magnified over 3,000 times by a scanning electron microscope.Sperm
While their utility is still under debate, fingernails, like fingerprints, are thought to be unique and thus useful in linking suspects to crime scenes. This is because the underside of fingernails and toenails have grooves, called striations, that form a pattern unique to each finger or toe; nails from one individual match up to their owner much like bullets fired from the same gun. Fingernail evidence has been used in several U.S. cases since the mid-1970s. Pictured here is a section of fingernail magnified over 300 times by a scanning electron microscope.Fingernail
Forensic scientists can analyze the DNA found in the cells of a single hair root to identify their killer or victim. Investigators often find hairs with roots attached at crime scenes, indicating a struggle took place. Pictured here is a color-enhanced image of a hair root, magnified over 90 times by a scanning electron microscope.Hair root
DNA can sometimes be obtained from skin cells that an attacker unwittingly leaves beneath the fingernails of a victim during a fight. In one case, police found a victim with hair clutched in her hand and skin under her nails; investigators were able to use this evidence to link her husband to the crime. Pictured here is a color-enhanced image of a healthy skin surface, magnified nearly 1,000 times by a scanning electron microscope.Human skin
Pollen — which can be breathed in, consumed or discovered on clothing — can have a lot to say to a forensic investigator. Tracing a pollen sample to its species of origin can indicate in what season a person died and what kinds of plants grew nearby, for example. This picture contains three types of pollen: daisy (prickly), cherry (oblong) and hornbeam (round). It was color-enhanced and magnified over 1,100 times by a scanning electron microscope.Pollen