The parents of American researcher Shane Todd have discharged their lawyers and informed the court on Wednesday that they will no longer be participating in the inquiry into their son's death.

This came after their application to delay a witness's testimony by a day was denied by the State Coroner on Tuesday. Their application was denied because the witness Luis Montes - a former colleague of Dr Todd at the Singapore Institute of Microelectronics (IME) - was due to return to France that evening.

Senior State Counsel Tai Wei Shyong explained to the court when the inquiry resumed on Wednesday morning that Dr Montes arrived in Singapore only on Saturday and his police statement taken on Monday.

The statement was given to the Todd family's counsel on Tuesday morning hours before he took the stand and lawyers for the Todd family had also agreed to question Dr Montes that day. But the lawyers later asked for an additional day to examine the evidence right before he took the stand, on instruction from the family.

State Coroner Chay Yuen Fatt said it was unfortunate that the Todd family viewed Dr Montes as a "surprise witness", but that the inquiry would continue.

The Todd family also met United States ambassador to Singapore David Adelman on Tuesday evening. A spokesman for the embassy would only say that the meeting took place at 5pm, and Mr Adelman offered the family his condolences and listened to their concerns.