Chris McKinney has pleaded not guilty to dangerous driving causing the death of Linda Varley.

He's accused of veering onto the wrong side of the New England Highway on February 28, causing a head-on collision between his Volkswagen and Ms Varley's Suzuki.

On the second day of the trial in Tamworth District Court, the court heard evidence from medical experts that it is "unlikely" the prescription drugs being taken by McKinney could have caused him to "black out".

McKinney's regular Victorian GP, Dr Sayeed Mohammed Khan, gave evidence that in the months leading up to the crash, McKinney had been taking a regular dose of certain prescription medications and had never complained about any side effects, nor shown signs that his blood pressure had been affected.

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Crown prosecutor Matt Coates asked Dr Khan if McKinney had reported any "dizziness" or "drowsiness" during several doctor visits in late-2018 and early-2019, when he was taking the medications.

"No," the doctor replied.

Dr Khan said that on multiple occasions in the months prior to the crash, McKinney had recorded "normal" blood pressure readings.

The court heard McKinney was rushed to Tamworth hospital after the crash, where he told the emergency doctor treating him that he "thought he may have blacked out".

Pharmacologist Ben Ryan, who examined McKinney's blood sample reports, told the trial that McKinney's claim he "may have blacked out" lacked medical proof.

He said two particular prescription drugs McKinney was taking could have possible side effects, but it was unlikely they would start appearing after the patient had been "stabilised" on the medication.

"It may cause dizziness or lightheadedness," he said.

"It's mainly an effect that occurs as a postural change to standing upright, not if you're just sitting there."

Mr Ryan said the suggestion that McKinney suffered an episode of low blood pressure, causing him to lose consciousness in the moments before the crash, "lacked scientific basis".

"The act of driving a motor vehicle is not expected to result in a number of positions enough to stimulate hypotension," he said.

Prescription painkiller oxycodone was found to be in McKinney's system in tests taken after the crash, but Mr Ryan told the court it was at a level consistent with the regular dosage McKinney had been prescribed for months by his GP to treat his existing back pain.

The Crown called on two witnesses who had been first on the scene of the crash, about 15km north of Bendemeer.

Tarryn Bryan told the court she was behind Ms Varley's red Suzuki when it crashed. She said she went to both cars to check if the people inside were okay.

When she approached McKinney in his grey Tiguan, she told the trial she found him in the passenger well.

"He was talking and he was conscious and he became a little more lucid as I talked to him," she said.

"Mostly just chit chat to keep him conscious and make sure he stayed conscious."

The court also heard from the police officer who had visited McKinney's hospital bed on March 9, last year, after the accused had been transferred to the John Hunter Hospital in Newcastle, to get an "explanation" for the crash.

Senior Constable Jason Wright recorded a note, which was signed by McKinney, which he partially read to the court on Tuesday morning.

"The accused said: 'the last thing I remember was stopping at a service station on the New England Highway at a roundabout near Armidale to use the toilet, the next thing I remember is being in Tamworth hospital'," Senior Constable Wright told the trial.

When asked how the crash happened, McKinney had told the officer "I have no idea" and when asked if he could have crossed the middle line, he replied "I can't remember".

The trial before Judge Mark Marian will continue on Wednesday.