One of two sisters killed in a crash on the Port Hills above Christchurch messaged a friend just seconds before the fatal accident to say, "Bro I'm going to die tonight", adding, "Haven't gone so fast around Port Hills before". 

Teenager driver Levi Fiddymont says the brakes on his Subaru WRX failed that night, while the Crown says he was driving too fast. 

Tayla Alexander, 17, died and her sister Sunmara, 15, suffered critical injuries in the crash on Summit Rd in Christchurch on November 27, 2019. 

Sunmara, an Ashburton College student, died later in hospital on December 13 on her 16th birthday. 

She had suffered extensive burns after the car's fuel tank ruptured and the battle to save her had meant multiple amputations due to infections. 

Sisters Tayla (left) and Sunmara Alexander. Photo / Supplied 

A teenage boy who was also a passenger suffered serious injuries and survived. 

Fiddymont, now 21, denies two counts of dangerous driving causing death, as well as one charge of dangerous driving causing injury. 

A jury trial, which is expected to take up to four days, began at Christchurch District Court this morning. 

In an opening address today, Crown prosecutor Sophie Bicknell said there was no evidence of brake failure on Fiddymont's 2011 Subaru WRX. 

The court heard that Tayla sent a text message to her best friend moments before the fatal crash to say, "Bro I'm going to die tonight". 

When her friend messaged straight back to ask why, Tayla replied at 10.54pm: "Haven't gone so fast around Port Hills before". 

"Omg Tayla!!!!" her friend replied. 

A minute later, at around 10.55pm, Fiddymont was doing approximately 110km/h, the Crown says, when he came to a moderate S-bend. 

Because of his speed, Bicknell said he failed to negotiate the first bend and the car crossed the centreline before crashing into the steep rock back. 

The car spun anti-clockwise down the bank on the other side and Tayla, who may not have been wearing seatbelt, was thrown from the backseat. She struck a steel roadside barrier and landed 28m away, dying from massive head injuries. 

The car came to rest 3m down the bank and Fiddymont and the male passenger managed to get out. 

But Sunmara, who was seriously injured, was trapped inside the vehicle. It caught fire when the fuel tank ruptured and she received significant burns before emergency services could rescue her, the court heard. 

The male passenger, who broke his collarbone, ruptured his spleen, and had a brain bleed, has no recollection of the crash. 

It was a "tragic accident", Bicknell said, but caused by Fiddymont's driving. 

His lawyer, Andrew McCormick acknowledged the "absolute tragedy" of the accident and the harm and sorrow it has caused the Alexander family. 

Fiddymont "carries a huge load", McCormick said, as he will always live with the knowledge that he was the driver of a car which caused the loss of the two young lives. 

He wasn't driving dangerously, the lawyer told the jury, and told people straight after the crash that his brakes had failed. 

Fiddymont, who says he was doing about 65-70km/h at the time of the crash, not 110km/h as the Crown says, said he pumped his brakes coming down the hill but there was nothing there. 

He says he tried to use his handbrake to slow down. 

In a police interview, Fiddymont later told police he was aware of the possibility of something called "brake fade" when driving in hills. 

It's up to the Crown to prove that his brakes didn't fail, McCormick told the jury. 

And he stressed to the jury to be careful about how they interpret Tayla's text message. 

The trial, before Judge Paul Kellar, continues. 

The girls' father Jason Alexander's last words to his only children were: "I love you and be good." 

He had left the family's Ashburton home to see his partner. 

The girls then snuck out of the house and headed towards Christchurch. 

Alexander had raised his daughters on his own since their mother moved to Australia 11 years before. 

He said the sisters were extremely close but had different personalities.