Banned trainer Ben Smith has told an inquiry he was suffering from mental health issues and excessively using alcohol and prescription medication at the time four of his horses returned elevated cobalt readings.

Racing NSW on Wednesday started its inquiry after two laboratories found excessive levels of cobalt in two race-day samples for the Smith-trained Iron Duke and Elaborate last August and a pair of non-race day samples for Group 1 winner El Dorado Dreaming and Tabrobane last September.

All samples were found to contain cobalt levels much higher than the 100mg/L threshold.

Racing NSW vet Dr Toby Koeing said there were no medical reasons for a horse to have those levels of cobalt in its system.

“It’s well established that cobalt is performance enhancing,” Koeing said.

Smith’s lawyer Paul O’Sullivan said it could not be proven that Smith did anything to improve a horse’s performance but rather improve its recovery.

Chief steward Marc Van Gestel chimed in: “Does recovery not lead to increased performance?”

Smith treated Iron Duke and Elaborate with legal substances VAM and hemoplex via a pre-mixed intravenous drip.

When stewards raided his stables in September he initially said he administered 25ml of each substance before later changing his story to 30ml.

“Why did you say that?” Van Gestel said.

Smith replied: “It was a long day and you asked a lot of questions. I gave an approximate answer.

“The whole day was too much for me. I was frightened and scared. I was extremely panicked.”

Smith described the period as being a “bit of a blur” because he was battling depression and substance abuse.

“That dependence affected his decision-making process at the time,” O’Sullivan said.

“His judgment may have been adversely affected.”

What made things more unclear for stewards was that Smith didn’t record any of his own treatments on his horses.

The hearing continues on Thursday at 9am, when four more people will be interviewed.