One day after accepting plea agreements from 13 parents in the US college admissions scandal, federal prosecutors dropped the hammer on 16 others, additional charges carrying heavier penalties.

The 16, including actress Lori Loughlin and her fashion designer husband, Mossimo Giannulli, were indicted by a federal grand jury on money laundering and mail fraud charges.

That stands in contrast to the 13 parents who agreed to plead guilty, before any formal indictment, to a single charge of mail fraud.

The additional money laundering charge for the 16 indicted parents formally doubles their maximum potential penalty to 40?years. Although any sentences close to the maximum penalties are considered highly unlikely, the additional charge and a?failure to admit guilt do raise the risk of significant prison time if there are convictions.

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Legal experts have admitted, however, that the unusual circumstances of the case ¨C the largest-ever college admissions scandal, with celebrity parents among the defendants, and varying circumstances for each ¨C make predictions about courtroom outcomes even more difficult than usual.

The scandal has ensnared 33 parents charged with paying bribes to falsify student sporting and academic credentials to win their children admission to top US institutions that include Yale, Stanford and Georgetown universities.

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The parents allegedly paid the bribes, ranging from tens of thousands of dollars to $6.5?million (?5?million), to help their children gain entry to the universities. Nine college coaches have been charged with receiving the payments.

The alleged ringleader, William Singer, a Los Angeles college admissions consultant who arranged the bribes, also has pleaded guilty. Mr Singer cooperated with the investigation by helping the FBI record his calls with the parents and coaches after investigators learned about his activities from one of the parents.

One of the 13 parents who agreed to plead guilty, the actor Felicity Huffman, issued a statement apologising to numerous parties including all US college students who had worked hard to win admissions offers legitimately.

But at least three other parents are of aggressively fighting the charges. One of them, William McGlashan Jr, an international private equity investor, was among the 16 parents indicted. Mr McGlashan was reportedly fired from TPG Growth, the company he founded, after he was named in the case last month.

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Two others ¨C Gregory Colburn, a San Francisco physician, and his wife, Amy ¨C also issued statements through an attorney promising to fight the matter in court.

paul.basken@timeshighereducation.com