The just-being-a-parent defense was at the heart of an open letter that playwright David Mamet posted last week in The Hollywood Reporter in support of the actor Felicity Huffman, a longtime friend and professional associate of his. She is charged with disguising a $15,000 bribe used to boost her daughter’s SAT scores as a charitable payment.

In the letter, Mamet derided the charges as blind to the “unfortunate and corrupt joke” of university admissions policies that favor the children of alumni and big donors.

“That a parent’s zeal for her children’s future may have overcome her better judgment for a moment is not only unfortunate,” he wrote. “It is, I know we parents would agree, a universal phenomenon.”

Martin Murphy, a lawyer for Huffman, declined to comment.

New York lawyer Murray Richman called the scandal “a crime without a cash benefit” and said parents may seek leniency by arguing they made no financial gain.

“Who was hurt? Society was, but a message will be sent, and these people have been embarrassed,” he said. “But nobody is going to jail on this one.”

How far parents can negotiate down any prison time will depend partly on how heavily involved they were in the scheme and how much money they paid, lawyers said.

Take Canadian dealmaker David Sidoo, who prosecutors say conspired with Singer for years to pay an impostor $100,000 to take the SAT for each of his two sons and continued long afterward with inquiries about the GMAT, the business school entrance exam. Such a long-term relationship makes an entrapment defense, for example, harder to mount.

Sidoo, the only parent indicted, is now on leave from his executive roles. His lawyer David Chesnoff, who has defended Robert Durst among others, said in an emailed statement that Sidoo would “contest both the legal and factual basis for the charge.” He declined to elaborate.

Also working against claims of being duped by Singer, and likely to spur a spate of pleas, is the trove of evidence investigators amassed in the form of recorded conversations, checks and emails, said Aloke Chakravarty, a partner at Snell & Wilmer and a former federal prosecutor who helped secure the death penalty for Boston Marathon bomber Dzhokhar Tsarnaev.