The university's Teachers College announced Wednesday it had imposed "serious sanctions" against Constantine following a lengthy investigation it said uncovered "numerous instances in which she used others' work without attribution in papers she published in academic journals over the past five years."
Constantine's lawyer, Paul J. Giacomo Jr., said his client could prove her innocence and called the school's investigation "extremely underhanded from the beginning." He said he would appeal the sanctions, which neither side would disclose.
The inquiry into Constantine, an education and psychology professor who has written extensively about race, was launched in 2006, long before the noose was discovered this past October, the school said.
"The investigators found a real pattern - two dozen instances of similar language from three people who came forward separately," Teachers College spokeswoman Marcia Horowitz said. "Dr. Constantine's explanation was not credible."
In a written statement, Constantine said she had been subjected to "a conspiracy and witch-hunt by certain current and former members of the Teachers College community."
Her lawyer said she had "clearly" been targeted because of her race, and he said he believed the noose incident and the plagiarism investigation might be linked.
"There's been an effort to intimidate my client, that's clear," Giacomo said.
Horowitz dismissed Giacomo's claims, saying "it is both absurd and untrue that racism had anything to do with this report."
"Teacher's College has zero tolerance for racism, discrimination or prejudice of any kind," she said.
Columbia said some of the plagiarized work was written by Christine Yeh, a former colleague of Constantine's who is now with the University of San Francisco.
"I'm really hopeful other people will come forward now," Yeh told The New York Times. "When the initial charges were made, there were many students involved who didn't feel they could follow up. They were too scared, and they were afraid of retribution."
When Constantine's colleagues discovered the noose, a symbol of lynchings in the Deep South, hanging from her office door, the incident roiled the Ivy League campus and gained national attention.
Police at the time ruled out any possibility that Constantine had hung the rope herself. A few weeks later, a swastika was discovered on the door of a Jewish professor at Teachers College.
Investigators have yet to make an arrest in either incident.