Stewards raided his stables last September after two horses had positive swabs.

"There was a lot of pressure being an up-and-coming trainer," Smith said.

Smith was stood down and faced an inquiry at Racing NSW headquarters on Wednesday into the excessive cobalt levels found in race-day samples taken from Iron Duke and Elaborate.

Early in proceedings, lawyer Paul O’Sullivan flagged that mental health issues would be part of the defence. Stewards took evidence in camera from Smith during the four-hour hearing.

O’Sullivan offered a doctor’s report about Smith’s mental health as evidence, telling stewards of Smith's excessive use of prescription painkillers for a back complaint and his drinking problem. He said it led to depression and anxiety.

Smith has been stood down since stewards raided his stables following two swabs that exceeded the cobalt threshold of 100mg/L. Both were outside the calibration of testing equipment. Iron Duke had a level of 245mg/L and Elaborate 535mg/L. Testing from the raid showed El Dorado Dreaming had 740mg/L and Tabrobane 2900mg/L.

Smith admitted to using a drip which had three times the manufacturer’s guidelines of VAM and hemoplex - legal substances that contain cobalt - five days out from racing. It was given to El Dorado Dreaming and Tabrobane the morning of the raid. 

Smith would then follow up for the next two days with three times another 30 millilitres of VAM and hemoplex, again three times above the recommended dose, delivered by injections.

However, he claimed he hadn't breached the rule that horses must not be treated one clear day before racing.

There were no records of the use of the drugs in Smith's treatment books, which had only been filled out by stable staff, not the trainer himself, who gave the drips and injections.

“We are flying blind here because you didn’t fill out your treatment book and depending on your memory,” chief steward Marc Van Gestel told Smith.

The trainer admitted to having been “slack” with his record keeping through his career. Smith said the use of hemoplex only started in August and stewards said looking at the records of his runners, the cobalt levels before the Iron Duke sample had been within normal levels.

O’Sullivan challenged the evidence of Racing NSW veterinarian Dr Toby Koenig, who challenged Smith’s intent. Smith claimed the drugs were being used for recovery.

The inquiry will continue on Thursday when two of Smith’s former staff, Shaun Flaherty (now a rider’s agent) and Neil Costello (who was warned off for failing to give evidence during the Smith investigation), are asked to attend.