A driver accused of hitting and killing a cyclist had allegedly used his phone 55 times shortly before the crash.

Shannon Turner, 32, fronted a South Australian court on Tuesday after hitting John Dennis, 72, on October 17, 2023.

The grandfather was killed just before his 50th wedding anniversary and was part of a group of cyclists near Port Pirie, 220km north of Adelaide.

Turner has pleaded guilty to causing death by dangerous driving.

The court on Tuesday heard Turner allegedly unlocked his mobile phone 55 times before hitting Mr Dennis, 7News reported.

He'd allegedly used Google, scrolled social media and online shopped. 

Prosecutor Kim Ballans alleged Turner had opened Snapchat 48 times and Instagram 13 times.

He'd allegedly taken photos while driving, viewed four videos and shopped for wireless chargers and car kits. 

Mr Ballans claimed the alleged mobile phone use while driving 'was not a once-off' but 'sustained, flagrant, prolific and shocking'.

Turner had not been injured in the fatal crash but his car's windshield was shattered and it sustained damage to the bonnet and front bumper.

Mr Dennis died at the scene.

Turner read a letter of apology to the court as Mr Dennis' wife, Julie, sat in the gallery.

The letter made no mention of his alleged mobile phone use.

'The hurt, the loneliness, the emptiness doesn't go away, the loss inflicted upon us will remain,' Julie told reporters.

The court also heard Turner's vehicle didn't brake before the collision.

Prosecutors alleged he didn't take evasive action or leave a 1.5m gap between his car and the cyclists while passing at 110km/h.

Turner will be sentenced at the end of the month.