Sam Bankman-Fried, the co-founder of failed cryptocurrency exchange FTX, testified Friday that many mistakes were made that led to the collapse of the business and the disappearance of $8 billion in customer money, but he denied that any fraud occurred.

Taking the stand in his own defense in his criminal fraud trial, the 31-year-old Bankman-Fried explained that FTX’s risk-management structure came unwound, but he attempted to couch that as a failure that resulted because the company had grown too rapidly.

“We thought we might be able to build the best product on the market and move the cryptocurrency system forward,” Bankman-Fried said in response to questions from his lawyer. “It turned out basically the opposite of that. A lot of people got hurt.”

But when asked directly if he had defrauded anyone, Bankman-Fried responded, “No, I did not.”

Bankman-Fried spent much of his time on the stand describing how FTX and its sister hedge-fund investment arm, Alameda Research, were built and how their systems were intertwined.