PC Paul McVeigh, 48, from Hebburn, denies twice attacking Nissan worker Jack Moore at Sunderland’s Southwick Police Station.
McVeigh is alleged to have dropped Mr Moore - who was handcuffed - face first on to a cell floor after the detainee spat in his face.
Mr Moore had been arrested for being drunk and disorderly.
A jury at Teesside Crown Court was shown CCTV footage of Mr Moore being dragged from the back of the police van at the police station and landing on the ground.
Jurors were then shown images of him being dragged into a cell and allegedly being thrown on to the cell floor.
He suffered a cut to his chin, which required 15 stitches, and blood was visible on the cell floor.
The jury was also shown footage of McVeigh with spit in his eye after Moore was arrested and put in the back of the police van following an incident in Washington, on January 26 2017.
It was filmed on a body-worn camera by PC Thomas Strawbridge, who was called to a house which drunken Moore had refused to leave.
PC Strawbridge told the court that Moore had been abusive and swore so he decided to take him in for being drunk and disorderly, and the single-crewed probationer called for back-up.
He said McVeigh arrived and they arrested Moore but he started to struggle and then spat in McVeigh’s face after the officers cuffed his hands behind his back.
McVeigh drove him in the van to Southwick and PC Strawbridge followed in his patrol car.
The younger officer said he put out a leg to break Mr Moore’s fall from the police van at Southwick when McVeigh pulled him out of the vehicle’s caged section.
When Mr Moore was taken into the holding cell, PC Strawbridge said he saw him skid 10in (25cm) along the floor after he landed face down.
McVeigh denies assault - in relation to dragging Mr Moore from the van - and assault occasioning actual bodily harm, for allegedly throwing him face first on to the cell floor.
The jury has heard that officers were not given spit-hoods to use on suspects.
Mr Moore later admitted charges of drunk and disorderly behaviour and assault in relation to the incident.
He also has a previous conviction for spitting at a police officer.
In a statement, Mr Moore said he had little recollection of the events.
The trial continues.