Jayant Patel either made a rash, fatal and criminally negligent decision to operate on a man who later died, or he was a busy doctor who tried his best to save a patient's life.

These were the two scenarios put to a Brisbane Supreme Court jury on Friday, as lawyers in his manslaughter trial summed up their cases.

Defence barrister Ken Fleming QC told the jury there was insufficient evidence to prove his client caused the death of 75-year-old Mervyn Morris after he removed part of his colon in an attempt to address rectal bleeding in 2003.

He said Patel had an "honest and reasonable belief" that the operation at the Bundaberg Base Hospital was necessary, and his actions were supported by a number of expert witnesses.

He urged the jury to treat with caution evidence from crown witnesses who used "the luxury of hindsight" to criticise Patel's decision to operate.

"Dr Patel didn't have that luxury," he said.

"He was making decisions as a very busy surgeon in a busy hospital where he had numerous patients."

However, prosecutor Peter Davis SC urged the jury to convict Patel, saying he had breached his duty of care by performing an inappropriate operation on a man who was too sick to survive surgery.

Mr Davis said only two of six surgeons who gave evidence supported Patel's actions, and one of those witnesses was Patel himself.

Mr Davis said Patel misdiagnosed the cause of Mr Morris's bleeding, misjudged the risks, ignored the patient's other health factors and provided inadequate post-operative care.

He said the behaviour was negligent and caused a patient's death.

The jury is expected to retire on Monday.