The phrase "after assertion" is correct and usable in written English.
It can be used in contexts where you are referring to something that occurs following a statement or claim made.
Example: "The results of the experiment were analyzed after assertion of the hypothesis."
Alternatives: "following the assertion" or "subsequent to the assertion".
But Mrs. Cowles's painting, which Mr. Gagosian took on consignment, was eventually sold for only $2 million after assertions by the gallery — disputed by Mrs. Cowles — that it was damaged.
Davis was arrested, charged with murder, and finally freed by Pakistan last month, after assertions of diplomatic immunity, weeks of secret negotiations, and millions of dollars paid to the victims' families.
But the painting was eventually sold for only $2 million after assertions by the gallery – now disputed in court by Mrs. Cowles – that it was damaged, and Mr. Gagosian made an unusually high commission on the deal, $1 million.
The hacking scandal had been smoldering for years, but ignited in recent weeks after assertions that hacking on behalf of The News of the World had interfered with the investigation into the 2002 murder of a 13-year-old girl, Milly Dowler.
Roux said the state had been wrong to pursue the charge of murder after assertions made at the initial bail hearing – that he was wearing his prostheses at the time he fired the gun, and that he was standing close to the toilet door as he fired into it – had been disproven.
And by giving the same speech to graduates at Liberty, Columbia University and the New School, Mr. McCain appeared intent on restoring his reputation as a straight talker, after assertions that he has been kowtowing to conservative Christians ahead of a presidential run.
That avenue of investigation was added in recent weeks after assertions by former FBI Director James Comey that President Donald Trump had tried to dissuade him from pressing an investigation into the actions of Trump's first national security adviser, retired Army Lt. Gen. Michael Flynn, members of Congress said, though it was not clear whom that part of the probe might target….
The NCS began after assertions from both the President's Task Force on Environmental Health and Safety Risks to Children and the Children's Health Act of 2000 that a multiagency consortium should carry out a large longitudinal study.
After his assertion he is Nakamoto, some sceptics demand technical proof.
