Anusha Ranganathan, 41, admitted death by dangerous driving and was today sentenced to two-and-a-half years in prison

An exhausted mother has been jailed for killing a 70-year-old grandmother who she slammed into a ditch after falling asleep at the wheel.

Anusha Ranganathan, 41, caused Patricia Robinson the 'most horrific' and ultimately fatal injuries when she veered her Toyota on to the wrong side of an Oxfordshire A-road and into the pensioner's car.

The impact threw the IT businesswoman's 18-month-old son from the back seat and into the footwell as flames engulfed the vehicle.

The baby and Ranganathan were both rescued and have since recovered but Mrs Robinson died five weeks later in hospital after rupturing 'almost every organ' in her body.

Ranganathan admitted death by dangerous driving and was today sentenced to two-and-a-half years in prison.

The court heard that the defendant had been kept up all night by her son who had undergone recent heart surgery.

Jailing her at Oxford Crown Court, Judge Ian Pringle said he could not accept that - because she drifted asleep at the wheel - the defendant did not realise she was too tired to drive.

And he added: 'When someone is driving a car and they fall asleep, it turns into a lethal weapon. This was a poor piece of driving to put it mildly.

'We will never know why you drove in the way that you did, but it seems that you fell asleep behind the wheel.

'Mrs Robinson suffered injuries described by doctors as the most extensive in a road traffic accident who had not died, and this was caused by you.'

Patricia Robinson suffered the 'most horrific' and ultimately fatal injuries when Ranganathan veered her Toyota onto the wrong side of an Oxfordshire A-road and into the pensioner's car

The impact threw the IT expert's 18-month-old son from the back seat of the Toyota (rear) and into the footwell as flames engulfed the vehicle which had crashed into the pensioner's Nissan (fore)

The judge heard that the horrific crash happened in East Hanney, Oxfordshire, with both cars ending up in a water-filled ditch.

'Ranganathan's car caught fire with her baby, who was a passenger, trapped in the footwell after falling out of his baby seat. Mrs Robinson died in hospital almost five weeks after the crash.

Prosecuting at Oxford Crown Court Jonathon Stone said: 'At 11.50am on July 4 there was a collision between the defendant who was driving a silver Toyota and the victim who was driving a white Nissan Duke on the A338 near East Hanney.

'The Toyota, carrying Mrs Ranganathan's young son in the rear of the car, veered onto the opposite carriageway and hit the Nissan head-on, causing both vehicles to come of the road and into a muddy ditch.'

The prosecutor read the statement of a lorry driver who had witnessed the incident, in which he said: 'I saw a silver vehicle drifting across the carriageway. I thought one of the drivers would turn away, but they didn't.

'I expected to hear some braking, but nothing happened. I was quite shocked,' said trucker Roy Lacey.

He described the tragic scene of three men desperately trying to help an elderly woman escape from her car that was filling with smoke from a fire that had started after the collision, but they could not get the door open because of the grass verge.

He said: 'I helped lift the car to allow two men to get the woman out. She was passed out, we were all worried.'

A police investigation concluded that it was not the weather, inappropriate speed, drugs or alcohol that caused the crash but either that Mrs Ranganathan was distracted or fell asleep at the wheel.

An emotive victim statement was read by Nolan Robinson, son of Mrs Robinson, who said: 'When I got the call that my mum had been in a car accident, I knew it would not have been her fault as she had a clean driving licence for 35 years.

'At 70-years-old, she still had so much life left in her and she did not deserve to die. Her (Ranganathan's) recklessness has cost us a mum, grandma, sister, niece, and an aunt.

'Nearly a year after the accident, she still has not apologised to the family.'

The judge lambasted defendant's decision to drive exhausted while her husband was also in the car

The prosecutor read the other brother's victim statement which said: 'My mother suffered the most horrific injuries. Every bone in her body was broken and almost every organ, apart from her heart and her head, was damaged. We all went through nearly five weeks of hell.

'When she passed away from her horrific injuries, it felt like my whole world had ended. I had to tell my children that grandma was gone. My whole life has been affected - my days are filled with depression and grief.'

Defence counsel Matthew Kerruish-Jones said in his mitigation that Ranganathan had, prior to the collision, a clean driving licence and had never been in trouble with the police.

He said: 'Road traffic accidents where there is a fatality are arguably the most emotive cases.

'It affects the family of the victim but it also affects members of the emergency services, the witnesses and the defendant, along with their family.

'The evidence shows that Mrs Ranganathan did not set out to cause an accident and cause a death of a human being. She ran a successful business and is highly regarded in the community.

'Evidence supports that there was a distraction or that she fell asleep at the wheel.'

The defence counsel moved onto read a downcast Ranganathan's letter to the court.

It said: 'When I set out to drive with my husband and son that day, I never imagined being the reason to cause so much hurt and pain to so many people. I shall feel remorse for as long as I live.'

During the mitigation, Judge Pringle referred to Mrs Ranganathan's character reference saying: 'I have rarely read a more impressive set of testimonies.'

However, he said that he found it difficult to accept that, for someone to fall asleep, they were not aware of feeling tired and that they did not stop when they noticed it.

Sentencing Ranganathan, of Grove, Oxfordshire, he said: 'When someone is driving a car and they fall asleep, it turns into a lethal weapon. This was a poor piece of driving to put it mildly.

'I am aware of the injuries you suffered as a result of the collision in which you stayed overnight in hospital, but they are incomparable to the horrific injuries suffered by Mrs Robinson.

'We will never know why you drove in the way that you did, but it seems that you fell asleep behind the wheel.

'Mrs Robinson suffered injuries described by doctors as the most extensive in a road traffic accident who had not died, and this was caused by you.

'The effect on Mrs Robinson's family has been devastating. I know as a mother you will be aware of how devastating that is.

'I understand that this is a one-off offence but this is the most serious outcome to have happened. I am sentencing you to two-and-a-half years imprisonment for this offence.'

Along with the custodial sentence, Judge Pringle disqualified Ranganathan from driving for three-and-a-half years and said that she will have to undergo an extended test before driving again. She was also ordered to pay a victim surcharge.