DEDHAM - The Karen Read case returned to court Thursday as a defense expert was on the stand for more than six hours, just so a judge could determine whether or not she can testify about alleged dog bites at Read's second trial.

Whether Dr. Marie Russell, an emergency doctor, should be allowed to testify in the Karen Read trial. The defense says she is an expert on dog bites.

The judge in the Karen Read case on Thursday heard statements from a medical specialist to determine whether she’ll allow the physician to testify at a retrial that the wounds on John O’Keefe’s arm appeared to have been caused by a large dog.

A hearing to determine whether the defense can use their preferred dog bite expert, Dr. Marie Russell, in the second trial of Karen Read took place in a marathon session that more resembled a

Whether Dr. Marie Russell, an emergency doctor, should be allowed to testify in the Karen Read trial. The defense says she is an expert on dog bites. Several people struggling with addiction in Charlotte, who’ve flown to drug rehab centers in California, say that when they got there – they didn’t get the treatment they needed.

At Read’s first trial, which ended with a hung hury, the medical expert told jurors that scratch marks on John O’Keefe’s arm appeared to come from a large dog.

The reason for the hearing was to discuss whether certain experts would be allowed to testify at Read’s second trial. Read is accused of hitting her boyfriend Boston Police Officer John O’Keefe with her SUV and leaving him to die in the snow outside a home in Canton almost 2 years ago.