The court heard from a sleep specialist who said falling asleep without warning was not a feature of sleep apnoea. 

Tim Ellis, SC, has pleaded not guilty to causing death by negligent driving in a three vehicle crash on the Midland Highway that claimed the life of a 27-year-old Launceston woman a year ago.

The prosecution allege Mr Ellis's driving was ``conscious and voluntary''.

Mr Ellis told police two days after the crash that he had no recollection of the first collision, and it was possible he was asleep, or had experienced the effects of sleep apnoea.

Dr Hugh Mestitz told the court this morning that falling asleep without warning was not a feature of sleep apnoea.  

Defence lawyer Michael O'Farrell, SC, asked Dr Mestitz: ''Is the fact that Mr Ellis was travelling down hill maintaining steering input on corners and met the Corolla head on consistent with the gradual onset of sleep and then complete sleep?''

Dr Mestitz replied ``I believe that is a scenario that's plausible, yes''.

A crash investigator had told the court that steering was required for Mr Ellis's car to stay in the lane it was in.

Dr Mestitz said it was not possible to steer a car and be asleep, but that it was possible to keep steering during the onset proceeding sleep. 

The trial continues this afternoon.