"Should the Court disagree that the Anderson declaration be excluded, the defense opposes any delay in sentencing and will address it on Friday to the best of the defense's ability under the circumstances, which are circumstances not of Maria's making," Butina's lawyers said in a court filing.
The evidence in question comes former FBI agent Robert Anderson, who claimed in a declaration to the court that Butina's work for the Russian government was of "tremendous intelligence value" and may have caused "significant damage to the United States."
US prosecutors included the declaration along with their pre-sentencing memo asking the court to sentence Butina to 18 months in prison.
READ MORE: US Prosecutors Seek 18-Month Jail Term for Russian National Butina
Butina, who has pleaded guilty to charges of conspiring to act as a foreign agent, has requested a sentence of time served.
Her lawyers argued in Tuesday's filing at the US District Court for the District of Columbia that it would be a violation of her right to due process under the law if the court allows the declaration to be considered during her sentencing hearing on Friday.
"Due process requires a defendant to have adequate notice of the evidence to be offered against her," Butina's lawyers said, calling for the declaration to be excluded from her hearing.
Allowing Anderson's testimony would transform the hearing “into a separate trial on unreliable claims with lower burdens of proof” her lawyers argued.
Not only was Anderson's statement disclosed unacceptably late, but it also included "unreliable information," they added.
A court document also revealed that US prosecutors in Maria Butina's case are prepared to delay her sentencing hearing scheduled for 26 April if defence lawyers need more time to review new evidence.
"Yet the government provided the defense with timely and adequate notice and, to the extent that the defense believes it needs additional time to respond, the government will not object to the Court providing them with that time," the prosecutors said in the court document on Tuesday.
Butina was arrested in Washington in mid-July last year on suspicion of working as an unregistered foreign agent for the Russian government.
The young woman initially denied the charges, but last December, she agreed to cooperate with the prosecution and pleaded guilty to one count of conspiracy to act as a foreign agent.
Both Butina's defence and US prosecutors have requested that Butina be deported immediately after sentencing.
