A long-running case that's ended with a Christchurch man convicted of murdering his childhood friend is being described as unique by a criminal lawyer.  

It was the second trial faced by former prison guard David Benbow over the disappearance of Michael McGrath in 2017. 

It followed an eight-week trial in the High Court in Christchurch. 

The verdict follows six years of investigation and two trials, one ending in a hung jury. 

Criminal lawyer Steve Cullen told Mike Hosking that this case has been on solely circumstantial evidence.  

But he says this can happen, and with such a small population in New Zealand, it can be easier to whittle suspects down. 

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