Forensics Science is the application of scientific knowledge and proof in matters of legal concerns. Same as the possibility of gene activity is found to be useful to determine the time of death of an individual.
Forensics Science is useful tool when it comes to cases in the courts of judicature and criminal laws during the criminal investigation, monitored under the standardized evidence during criminal activities.
Forensics science is being applied to investigations since the thirteenth century and thanks to the continuous advancement in science and technology, Forensic Science has developed gradually. Recently, the possibility of Gene activity is found to be useful to determine the time of death of an individual. Post-mortem examination of tissues significantly aid in the investigation to determine Gene-Expressions.
Researchers stated that the RNA-sequencing showed changes in the Gene expressions of some particular human tissues shortly after death. Through further indulging, Professor Roderic Guigo (Computational biologist, Centre for Genomic Regulation in Barcelona) and his colleagues found that the blood sample of and individual’s pre and post-mortem had different transcriptions. Then the scientists were able to bring about a model in order to predict the time of death, given that some specific tissues are accessible.
Just like, when we are boiling something and we turn off the flame in the middle, it still bubbles away but at a slower rate, similarly death isn’t the immediate end for the genes. Some remain active for up to hours or days after the person has died.
RNA usually known as weaker or unstable, single stranded molecule as compare to DNA, is a surprisingly stable molecule, according to a recent research. Some genes in our DNA are still transcribed into RNA, even after the body has deceased. Brain is not needed for gene expression. Processes at molecular level can still continue until necessary enzymes and chemicals don’t run out.
Professor Guigo along with his team, took 36 specific types of tissues from 540 individuals at different time after the person has deceased and observed gene activity whether it had rose or fell. Although gene activity in tissues like the muscle tissue stopped right after the blood flow stopped. But in some other tissues it not only continued but the activity level also increases. Elevated levels of mRNA were observed when gene activity rose.
One of the gene that ramps up is HBA 1 that encodes the type of hemoglobin that distributes oxygen around the body. It increases in ten tissues including that of esophagus, testis and colon. After the body has deceased and the blood stops flowing, cells might increase the hemoglobin formation to pull out what little amount of oxygen is left as reported by Professor Guigo.
After this researchers then shortlisted types of tissue to the smallest combination that could best predict the time of death. They then derived only four types of such tissues: sun exposed skin, fat underneath the skin, lungs and thyroid.
But the question is how do scientists measure gene activity in a given human tissue sample?
They were able train a machine to learn algorithm in order to analyze mRNA data that predicts the time between death and when the tissue were collected. However the predictions were not found to be perfectly accurate but gives results close to tentatively one hour. It is an open sourced software and is an approach that complements the forensic methodology as illustrated by Professor Guigo.
Different tissues in different parts of body respond in different ways, for example brain cells depicts little changes whereas greatest changes are seen in the readings of lungs and thyroid but accuracy decreases when the time after death extends beyond 24 hours.
Other ways to assess how long the body has deceased is by measuring body’s deep internal temperature, the level of stiffness of muscles, electrically stimulating face muscle to measure excitability, potassium levels in fluid of the eyeballs and taking stock of maggots. But of course there is always a room for error as science has always been inexact. For example body temperature may vary by 2.8 hours
Medical examiners can also use changes in microbial community during decomposition. Between twenty four hours after the body has deceased, bacteria, unlike genes doesn’t show much changes. Hence changes in genetic activity can be more beneficial to trace back how long the person has died but at longer scales, microbes may work better.
Authors: Fattimah Saeed Taj, Maira Sohail, Areesha Ghani