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Detecting Evidence After Bleaching

By: Ian Murnaghan BSc (hons), MSc - Updated: 10 Aug 2016 | comments*Discuss
 
Forensics Bleach Evidence Blood Stains

Most people know that forensics involves many different kinds of evidence, whether that is blood evidence or a weapon. However, the evidence can become degraded from a number of things such as time, heat or the use of bleach. Unfortunately, even advanced Forensic Techniques can be challenged by the use of a common kind of bleach found in many homes.

Understanding Bleach And Evidence

To understand how it all works, you have to consider that there are two kinds of bleach that are found in the majority of cleaning products within your home. There are bleaches that are primarily chlorine and there is also oxygen bleach.

Chlorine bleaches can remove a Bloodstain to the naked eye but fortunately, forensics experts can use the application of substances such as luminol or phenolphthalein to show that haemoglobin is present. In fact, even if the shady criminal washed a bloodstained item of clothing 10 times, these chemicals could still reveal blood.

With oxygen bleach, the bleach has an oxidising agent, which could be a substance such as hydrogen peroxide. In these instances, haemoglobin is completely removed and can't later be detected. As expected, this presents a unique challenge for forensic scientists. Not only that, but it can significantly compromise an investigation and may mean that Evidence is not properly investigated and used in a trial.

Testing Out Bleaches

To properly assess whether bleach could fully remove blood, researchers soaked some bloodstained clothing in oxygen bleach for a couple of hours. After the bleaching, stains did look faded, although they were still somewhat noticeable. On the other hand, even though there was some visible marking, luminol and phenolphthalein didn't detect the haemoglobin on the clothing.

Challenges Of Detecting Bleach

The results are worrying because a stain on clothing could be assumed to occur from something else when a test shows up negative for haemoglobin. Eventually, valuable evidence could ultimately be dismissed, which then affects the entire criminal investigation and trial proceedings.

Forensics experts will not examine and check for important DNA Evidence until they have initially found an appropriately identified blood sample. In this way, the entire investigation is compromised and the opportunity to obtain more information is lost.

Fortunately, there is a better chance of obtaining useful information from the seams of clothing. While washing does remove a great deal of evidence in the rest of the garment, it is far more challenging for a criminal to remove evidence found in the clothing seams.

Improving Forensic Science

The study is an important one that highlights the limitations and scope of forensics techniques in science today. Clearly, we have many advanced and sophisticated tools to investigate blood evidence.

Yet, science can't always compete with materials used to remove these stains, such as oxygen bleach. However, it is at least a positive step that we can identify these challenges, which means that efforts can be focused on finding ways to overcome them and identify blood even after all kinds of bleaching. In the end, this is good news for forensics but bad news for criminals.

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