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Determining the Age of Bloodstains

by georgemelcher

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CSI and real-life forensics are two different worlds, as a complex crime can't be solved as fast and quick as on TV. But it doesn't mean that most crimes will go unsolved; it's just that such things take time due to the sensitivity of evidence. Forensic labs often enlist the aid of state-of-the-art gear to help them put the pieces together.

When handling bloodstain evidence, a near infrared spectrophotometer light can be of great help to investigators and forensic scientists. Bloodstains most often appear in certain crime scenes such as murder and rape, and are vital and helpful for evidence purposes. The age of the bloodstain can predict not only the time of the crime's occurrence, but how long the body has been at the scene as well. Brown bloodstains mean that the crime happened days ago, given the change in hemoglobin.

A joint study conducted by the University of Rhode Island and Rhode Island College looked into NIR as a forensic asset. For one month, they put blood samples taken from veins and capillaries on gauze and glass. Apart from discovering that it's as effective as other methods of sampling bloodstains, NIR also solves a common issue with such tests: portability.

Before NIR, some of the most widely used means of analyzing bloodstains were atomic force microscopy and high performance liquid chromatography. But researchers argued that these methods took up too much time and cannot be utilized in the field. Since the urgency for results is a top priority in any crime, NIR technology has become a more popular option due to portable units that forensic investigators can use.

On another note, the chemical change in blood samples is caused by converting deoxyhemoglobin to methemoglobin. This is a result of the blood's exposure of to air, turning its color to brown just like rust in metal. In this case, the primary function of near infrared reflectance is to determine the timeframe of the chemical change from bright red to rusty brown, thereby giving an estimated time for when the crime took place.

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