DNA samples consistent with all three murdered Singh siblings were detected on a garden fork that police found hidden in their family home's garage, a court heard today.

In Supreme Court in Brisbane, Justin Anthony Howes, a DNA expert from Brisbane's John Tonge Centre, said various major and minor DNA profiles consistent with Neelma Singh, Kunal Singh and Sidhi Singh were found on the front and back of the garden fork's tines.

Mr Howes was giving evidence on the 60th day of a trial in which Max Sica, 42, has pleaded not guilty to murdering Neelma Singh, 24, Kunal Singh, 18, and Sidhi Singh, 12, at Bridgeman Downs, on April 21, 2003.

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The trial has heard police found the fork behind a barbecue in the garage several days after the murders.

Mr Howes explained that in various samples there was a major profile for each sibling on at least one occasion.

But in some others the minor profile could have been either Neelma or Sidhi because they were sisters.

Scientists had been unable to get any identifiable DNA from the fork's handle.

Mr Howes told the court bleach could have a major impact on the collection of DNA at crime scenes.

The trial has heard police alleged whoever killed the Singhs had tried to sterilise parts of the house with bleach.

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Garden fork held DNA of all slain siblings