The amount Dr. Salomon Melgen stole will help determine the length of his sentence. The government said its estimate is based on a random sample of 310 patients.
But University of North Florida math professor Donna Mohr testified Wednesday the sample wasn't random, making the extrapolation faulty.
U.S. District Judge Kenneth Marra didn't say whether he will accept Mohr's testimony.
Marra had been expected to sentence Melgen on Thursday after both sides make arguments, but the judge said Wednesday he might need more time to decide the sentence.
The 63-year-old Melgen could get life; his lawyers want less than 10 years.
He is separately charged with bribing New Jersey Democratic Sen. Bob Menendez.
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