A former Bixby Energy Systems executive who is testifying at the company founder’s fraud trial faces another day on the witness stand Monday — and it may be his toughest yet.

Dennis Desender, a former chief financial officer and fundraiser for the defunct Ramsey-based company, finished his third day of testimony for the government Thursday in U.S. District Court in St. Paul.

On Monday, Desender faces cross-examination by attorney Peter Wold, who is defending former Bixby CEO Bob Walker against charges of fraud, conspiracy, tax evasion and witness tampering.

Desender helped Walker raise $57 million from 1,800 investors from 2001 to 2011. The company once sold corn-burning stoves and then pitched a clean-coal technology, but Desender described the business as mostly focused on raising money from investors to enrich insiders, especially Walker and his family.

Walker, 71, is best known as the founder of bedmaker Select Comfort. But the trial before U.S. District Judge Susan Richard Nelson has offered a starkly different picture of a man who associated with felons like Desender at Bixby to promote technology that didn’t work.

Wold is expected to attack Desender, who has a felony record for bank fraud and embezzlement from the 1990s, and blame him for Bixby’s failure. The defense team contends that Walker was an entrepreneur and dreamer who wanted his alternative energy ideas to succeed, but was let down by others.