June 1: Model Sonika Singh Chauhan died from internal bleeding caused by two knocks to the head when the car she was in with actor Vikram Chatterjee crashed along Rashbehari Avenue early on April 29, states the post-mortem report. Forensic experts say she might have lived had she been wearing her seat belt.

The right side of Sonika's head possibly rammed against the steering wheel or the dashboard and the left side hit a window under the impact of the crash. She had only two other injuries, both minor, and her vital organs were undamaged, the post-mortem report has revealed.

Since Sonika did not fracture her skull or vertebrae either, forensic experts believe that she could have escaped the brain injuries that killed her by fastening her seat belt.

The police had said on Tuesday that Vikram, who was at the wheel of the Toyota Corolla Altis with Sonika beside him, was wearing his seat belt at the time of the crash.

Sonika's post-mortem report, a copy of which is available with Metro, suggests that there was leakage of blood from the vessels into the surrounding tissues on the right side of her head, covering the "right frontal (lobe) to right occipital region" that measures around five inches by four inches.

The right frontal lobe is the front part of the brain to the right while the right occipital region is the area behind the right ear. The second injury, measuring around two inches by two inches, was reported in the "left temporal region", which is the area above the left ear. Both injuries were concealed in nature.

Sources said Sonika was bleeding from her nose and ears because of these internal injuries.

The post-mortem report mentions that there was "diffuse sub-dural haematoma covering both cerebral hemispheres, including their under surfaces". According to a forensic expert, this means that there were blood clots inside the brain that diffused to both hemispheres.

"As the injury on the right side of her head was bigger than the left one, it suggests that the right injury could have been the primary one. It also means that her head had first hit either the steering wheel or the dashboard on the right and then snapped towards the left and hit the window as a reflex action of the first impact. It follows Newton's third law that every action has an equal and opposite reaction," the forensic expert explained.

Another forensic scientist with expertise in vehicle crash tests said that a seat belt, if fastened properly, restricts "free movement" and thus reduces the chances of injuries during an accident. All of Sonika's vital organs - heart, lungs, spleen, kidneys and liver - were in "healthy" condition but either "congested" or "mucous membrane congested", according to the post-mortem report.

The document will become a piece of primary evidence in court. The police have replaced the charge of "causing death by negligence" against Vikram with the stronger "culpable homicide not amounting to murder".