An emergency medicine specialist testified Monday in the Thomas Valva murder trial that hypothermia decreases a person's survivability.

The prosecution called Dr. David Saintsing to the stand to counteract Dr. Kenneth Zafren – a defense witness who testified on Friday.

Saintsing, who prosecutors say is an expert in hypothermia, also told jurors that it's 80% more likely that someone with severe hypothermia is going to go into cardiac arrest.

The Colorado doctor said there would be a "dismal expectation for survival."

Thomas Valva's father and his ex-fiancée have been charged in the 8-year-old's murder. Prosecutors claim they forced him and his brother to live in the garage for months - even when it was below freezing.

Zafren had said in an earlier testimony that a hypothermic patient with no detectable vital signs could still be resuscitated.

Defense attorney Anthony LaPinta says Dr. Saintsing was not a qualified hypothermia expert.

"So I think it's very clear that this witness has very, very little, minimal experience in hypothermia," LaPinta says. "It was just so abundantly clear from cross-examination and hence, I don't think any of the conclusions he's reached regarding hypothermia should be given much weight at all."

Prosecutors say Thomas Valva's body temperature was around 76 degrees the day he died. They say he was brought outside by his father Michael Valva and sprayed down with a hose.

The father has pleaded not guilty to the charges he is facing.

The judge says closing arguments should be wrapped up by the end of the week.