The burly Bernard B. Kerik of old may not have recognized the newer, slimmed-down version who showed up to speak to an impressionable group of aspiring police officers in Queens on Saturday morning.

This Mr. Kerik was subdued, clean-shaven: not exactly the hard-bitten law-and-order man whose cocksure approach fueled an unlikely rise from beat cop to corrections and then police commissioner, jet-set consultant, and the Bush administration’s choice to lead the Department of Homeland Security in 2004.

He showed less of the lock-’em-up bravado, the swagger during his law-enforcement career, before a series of ethics violations led him to plead guilty to fraud charges in 2009 and he spent three years in a minimum-security prison in Maryland. Released from prison in May, he is now on probation.

“Today I’m a convicted felon,” Mr. Kerik, 58, told the class.

After several years avoiding interviews, Mr. Kerik is now seeking attention. He has ideas for reforming the federal criminal justice system — easing mandatory minimum sentences, for example — that are born of personal experience. He wants to rehabilitate his reputation and build a new career as a speaker and consultant.

“Will people stay away from me now? I don’t know,” he said outside the classroom at Queensborough Community College, adding that he would speak to a conservative group in Washington this week about reform.

His life on both sides of the prison bars gives him a singular perspective into the criminal justice and prison systems, he said.