DNA Profiling: How it aids in solving crimes and catching criminals

By: Emmariel Ares - Multimedia Reporter - CDN Digital | November 24,2023 - 01:40 PM

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CEBU CITY, Philippines – Over the decades, DNA profiling has contributed to the resolution of countless criminal cases and put criminals behind bars to give justice to their victims.

Historical data shows that this process has become a significant part of the criminal justice system since it was first introduced to the world.

DNA, or Deoxyribonucleic Acid, is a molecule in every living being that carries their unique genetic code that makes them who they are.

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Often called the “blue print of life,” the DNA contains all the information that a being needs to function and reproduce.  

And because it is a hereditary material that supplies unique genetic instructions, no two persons have the same DNA unless they are identical twins.

DNA profiling

The analysis of DNA is widely used in various fields in society with one of them being forensic science. Through DNA profiling, biological samples are processed in order to identify either victims or suspects in crime scenes.

But how does this state-of-the-art procedure actually work? And what exactly is it’s significance in the world of forensic science? 

To provide more insight on this, CDN Digital spoke with Police Colonel April Carbajal Madroño, regional chief of the Regional Forensic Unit (RFU-7).

Police Colonel April Carbajal Madroño, regional chief of the Regional Forensic Unit 7. | Emmariel Ares

According to Madroño, the history of DNA profiling goes way back in the year 1988 when the Federal Bureau of Investigation started DNA case work. 

In 1995, a DNA data base was established in the United Kingdom. And three years later, the Combined DNA Identification System (CODIS), wherein DNA samples are collected from individuals, was introduced in the United States of America.  

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In the Philippines, however, a DNA Analysis Laboratory was opened by the Philippine National Police (PNP) in 2001. But it was in 2007 that the rules of DNA evidence was approved by the Supreme Court.

And since then, DNA profiling has revolutionized the country’s criminal justice system.

DNA case processing

Madroño relayed that there are specific steps that need to be followed in DNA case processing, namely:

  1. Collection of Evidence 
  2. Documentation chain of custody 
  3. Collection techniques
  4. Preservation of evidence
  5. Packing and storage

When police investigators, with the help of Scene of the Crime Operatives (SOCO), are able to collect genetic samples from crime scenes, these are carefully collected and put inside proper tools to prepare for transport. 

The biological samples that can be used for DNA extraction include blood, semen, saliva, urine, feces, hair, teeth, nail clippings, bone, tissue and cells.

These samples are analyzed in order to come up with the genetic code that will match to a person’s DNA. This way, authorities can identify a possible suspect or remove a person from pool of suspects. 

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When blood is collected from the scene, the sample is dried and stored in a paper container instead of a plastic one in order to avoid decontamination, according to Madroño.

And for possible victims of rape, it is police standard to collect vaginal swab. 

Then, the sample is transported to the laboratory to be analyzed by their DNA analysts.

In the Regional Anti-Cybercrime Unit in Central Visayas (RACU-7), there are a total of 3 DNA analysts with 3 DNA technicians working to process samples from Central Visayas. Their office also caters to PNP offices from Region 6 and 8.

Inside the laboratory, the samples will undergo analysis using advanced technological equipments.

The different steps that go into DNA analysis are: 

  1. Screening 
  2. Sampling
  3. Extracting of DNA
  4. DNA amplification
  5. Running of samples for visualization
  6. Data Interpretation
  7. Report Making

The authorities extract the DNA from cells in bodily fluids or tissues and copy it. 

Through a process called capillary electrophoresis, the copied markers are then separated. This allows them to identify distinct markers and the number of repeats for different markers in each allele. 

They read this data using a chart known as an electropherogram. This plots fragments of DNA and shows how many repeats there are for each marker and where they occur. Based on this, they generate a DNA profiling definition that can be read to identify possible suspects.

The DNA will then be compared to DNA samples of previously arrested persons which is stored in their database, as part of the standard procedure.

“Our forensic scientist can compare the DNA found at the crime scene from samples taken from the suspects. If there’s no match, they will be able to rule out the suspect. Kung hindi siya ang tinutukoy nung sample, so they can eliminate him as a suspect. If there is a match, police will likely want to take a closer look,” stated Madroño.

Madroño also highlighted the importance of proper handling and storage of the samples in order to avoid deterioration and decomposition which leaves the sample unusable. 

Why is DNA profiling important?

According to Madroño, this technology has revolutizoned the criminal justice system in the whole world because it has made it easier to identify suspects with less doubt on its accuracy. 

Unlike statements from eyewitness which are not always reliable, DNA profiling results are science-based, fast, and indisputable.   

It also decreases the chances of committing errors that end up putting innocent people behind bars. 

DNA profiling has been utilized to prove innocence or guilt, identify missing persons, examine parental relationship, and many more. And during mass disasters, this technology has been used to identify victims.  

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As an example, Madroño stated a previous case in Negros where police found blood  in the crime scene and a shirt with blood, hair, and sweat in a faraway area which allowed them to find the suspect. 

She also cited a previous murder case wherein blood was found in the nails of the female victim that was killed.

When two suspects were arrested a week after, their swab was taken and compared to the blood that was initially found.

Through this, they found that one of the suspect’s results came back positive which allowed them to dig deeper into the reason why the blood was there. In the end, the man was proven to be guilty of killing the girl and so he was sent to jail.

Despite DNA profiling being a tedious and expensive process, Madroño stated that it helps greatly to bring justice to victims of criminals in the country. 

One or two pieces of samples may take 2-3 weeks of processing while a bigger number will take longer. 

DNA profiling may be an important part of modern criminal investigation but it is important to note that it is not the only one.

However, this highly-advanced process will continue to aid criminal investigations in the years to come, according to Madroño.

“It is very important because dito sa criminal investigationn, we want to prove that the suspect was really involved in the occurrence of the crime. The investigateors would want to establish the link between the suspect, the victim, and the crime scene. That’s why it’s very important. Kung meron kang DNA analysis or DNA laboratory capability, matutulungan natin ang imbestigador sa kanyang pag-iimbestiga,” stated Madroño.


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TAGS: crime, criminal, Justice, police

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