A defence lawyer for Liam Jurrah has questioned the reliability of witnesses in the assault trial of the former AFL player at Alice Springs.

Jurrah, 24, has pleaded not guilty to unlawfully causing serious harm to his cousin Basil Jurrah, 35, in a fight between rival families at the Little Sisters town camp last year.

Defence lawyer Jon Tippett QC told the Northern Territory Supreme Court jury that witnesses in the case fell into several groups: those who truthfully said the wrong thing, witnesses incapacitated with alcohol, witnesses with a motive, and witnesses who were mistaken.

He asked the jurors to acknowledge the problems associated with unreliable evidence and witnesses.

He said Basil Jurrah was not forthright in giving evidence and some other witnesses were "lying through their teeth".

Mr Tippett told the jury Liam Jurrah was also a victim in this case.

Yesterday, he launched his summation with an attack on the police investigation, saying there was no crime scene, no one was looking for discarded weapons and there was no medical evidence linking the weapons to the type of injury Basil Jurrah received.

He said the investigation was neither objective or detailed.

He said Jurrah had been open with police, having nothing to fear because he had done nothing wrong.

Earlier, the prosecution had asked the jury not to look at witness testimony in isolation.

Prosecutor Stephen Robson reminded the jury to take into account all witness testimony to get the whole picture.

He said people recorded information in different ways but the core of the evidence was the same.

He said three of five witnesses said they saw Jurrah hit Basil Jurrah on the head with a machete, and two others said they saw Jurrah with a machete but did not see him hit his cousin.

The trial continues.