Satnam Singh, 74, was found with serious injuries in a Derby street in July 2015 - opposite the Sikh temple where he volunteered.
Police initially thought he had been hit by a car but last year arrested 30-year-old Sukhraj Atwal for murder.
Mr Atwal denies the charge. His defence said there was a lack of "real evidence" and witnesses.
The prosecution has previously alleged Mr Singh - the defendant's former step-grandfather - was "brutally assaulted" over a long-running family dispute.
The trial at Nottingham Crown Court claimed Mr Atwal repeatedly stamped and jumped on Mr Singh in the early hours of 23 July.
The victim was found with 41 fractures to his ribs, lacerations to his heart, a fractured skull and severe brain damage.
The attack itself was not captured on CCTV but Mr Atwal's car was seen entering and leaving the area shortly before Mr Singh was found.
Defending barrister Shaun Smith, said the case was based on "half-baked theories" and "speculation".
"There is no footage of what happened," he added.
"There are no eye witnesses and when it comes to real evidence there's nothing.
"Nothing to place him at the scene on his footwear or his car, no-one to hear or see it [the attack], or hear cries of distress or see anyone run into a car."
He said although the victim and defendant lived just streets apart "they ignored and blanked one another" and "barely knew" each other.
Mr Atwal chose not to give evidence in court.
The trial continues.

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The Ospreys scrum-half, 26, went down in agony after his leg was caught in a ruck against Italy and he was taken off the pitch on a stretcher.
Webb has had surgery on his damaged foot but the injury was so serious he will also miss the 2016 Six Nations.
"It hit me straight away, I was an emotional wreck as soon as it happened to a couple of days after," Webb said.
"I still think to myself now: 'How am I here and the boys are playing?' But I'm back driving, back in the gym now.
"The amount of pain I was in I knew straight away that my World Cup was over.
"I'd worked so hard over the last two years, with my goal getting that number nine shirt and obviously another one was playing in the World Cup in this country.
"Seeing that go out the window by one freak accident, I was pretty heart-broken."
Wales' opening wins over Uruguay and England have put them in a strong position to reach the quarter-finals - and Webb says he has been cheered by those victories.
Last season's Pro12 player of the year has now set himself the target of selection for the 2017 British and Irish Lions tour to New Zealand.
"I've picked myself up slowly seeing the boys win like they have done and playing well - it's just looking forward now.
"My long-term goal is British Lions - that's everybody's dream - but I need to set some shorter goals so I'll do them in a couple of weeks maybe."
Webb was back among his Wales team-mates on Wednesday as he and fellow injury absentee Leigh Halfpenny - the full-back ruled out of the World Cup and Six Nations with a knee injury suffered in the same game - presented the match jerseys for Thursday's game against Fiji.
"It was obviously a special occasion," Webb added. "I gave a bit of a speech, which was nerve-wracking, but it was very good, I enjoyed it - I was more nervous presenting the shirts than playing.
"Dan Lydiate and Toby [Taulupe Faletau] are winning their 50th caps so it was a pleasure to present them with their jerseys as well."
The trial of a man accused of murdering a pensioner in the street has heard he "had no motive" to kill him.
[NEXT_CONCEPT]
Rhys Webb says he knew his World Cup was over the moment he was injured in Wales' final warm-up match.