How does the forensic light that appears so often in The Assunta Case work?

IN Assunta case An element that was essential to the investigation of the crime is mentioned several times: forensic light. Thanks to her, it was discovered that there were traces of something that could be sperm on the girl’s shirt. Traces of liquids were also found in a vegetable garden at Montuto’s farm. The device was mentioned several times during the investigation of the case, as well as at trial. But what is forensic light?

It makes sense that this is something that exists in reality since it is still a true story. Although it may be given other names, forensic light is basically UV and blue light flashlight which is used to conduct the first examination of the crime scene.

Some fluids, such as semen, fluoresce when exposed to radiation of about 450 nanometers, which is blue light but very close to the limit of ultraviolet radiation. Other liquids, e.g. blood, they cannot be seen directly under forensic light. However, they can be detected by spraying a substance called luminol on the area. Except bleach Yes, it is detected directly by the flashlight, such that if an attempt was made to eliminate the evidence by cleaning with this disinfectant, it can be detected.

With forensic light, the first signs can be seen, but it is necessary to know exactly what substances caused the fluorescence. send tests to the laboratory. This is exactly what was done with the Assunta case, as we see in the series.

Forensic Applications

There are now forensic flashlights that can select a desired wavelength to limit the possible range of samples it can detect. However, traditionally they consisted of ultraviolet and blue light flashlights.

Different types of liquids react differently to this light. For example, some of them, such as sperm, are capable of emit fluorescence. That is, it absorbs light with a certain wavelength, in this case 450 nm, and emits light at another. As a result, it appears to glow.

In other cases, light is absorbed and not emitted, causing the spot to appear black. This happens, for example, with blood. If during the first inspection there are suspicions about presence of bloodyou can spray the area with luminol.

It is a compound which, upon contact with an oxidizing agent such as hydrogen peroxide and the hydroxide providing the basic medium, is little by little oxidized, generating energy in the form blue light. This is a very slow process. However, upon contact with iron, the reaction is greatly accelerated, occurring almost instantly. Blood contains iron. Therefore, if a solution of luminol with hydrogen peroxide and hydroxide is applied to a blood stain, it will quickly turn blue. You don’t need to use forensic light to see this, but the evidence can be complementary.

Laboratory analysis on the Asunta case

As we have seen, forensic light is very useful for preliminary examination of the crime scene. In Asunta’s case, something was seen shining under the blue light on his shirt. Forensic experts said it could have been semen, as well as other bodily fluids. Even bleach.

Laboratory analysis showed the presence of semen, but it was concluded that this could be due to contamination of the samples.

Be that as it may, one thing is clear: neither forensic light nor luminol can give definitive results. If fluorescence or lack thereof is detected, samples must be analyzed. Several years ago, when PCR began to be used to determine the origin of fluids such as blood, there were concerns that luminol could destroy DNA in such a way that PCR was not viable. However, studies conducted in this regard have shown that this is not the case. Both tests can be used together without affecting the results.

For this reason, forensic light is still used today. in combination with luminol or without it. But subsequent laboratory analysis is still necessary.