"I have found Liam to be a very honourable person, a very serious person," Mr Lewin told the Alice Springs Supreme Court where Jurrah is facing assault charges.
Jurrah has pleaded not guilty to seriously harming his cousin Basil Jurrah in a brawl in March last year. If convicted, he could face up to 14 years' jail.
As the trial entered its seventh day on Tuesday, Mr Lewin was called by the defence to give character evidence about the footballer.
He said he had known Liam Jurrah for more than five years, since the footballer was playing for the outback team the Yuendumu Magpies.
Mr Lewin is also president of the Collingwood Industrial Magpies, a charity group that aims to support indigenous people in sport.
Liam Jurrah had never drunk alcohol in his presence and lived quietly, Mr Lewin said.
"He did not go out socially with other footballers in ways I think we are all aware of," Mr Lewin told the court.
He said the footballer was a quiet, retiring, shy, polite, respectful, honest and forthright person.
Jurrah also carried considerable responsibilities for the Warlpiri people and the people of Yuendumu, Mr Lewin said.
Earlier, the court heard Jurrah was involved in two violent incidents at the Little Sisters town camp in March 2012.
Several witnesses have alleged the footballer hit his cousin with a machete, while other witnesses say they saw him walking around with various weapons on the night in question.
The prosecution case against Jurrah is expected to finish on Tuesday.