RIVERSIDE, Calif. (Reuters) - A California couple accused of keeping 13 children imprisoned, chained and starved in a squalid suburban home were hit with additional charges on Friday as defense lawyers said they were overwhelmed by the sheer amount of evidence in the case.

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David Turpin, 57, and his wife Louise, 49, were advised of the new charges during a brief hearing in Riverside County Superior Court at which they appeared dressed in black at a table with their attorneys but did not speak.

A spokesman for the Riverside County District Attorney’s Office said the new charges included three counts of child abuse against both defendants. Louise Turpin was also charged with felony assault.

“Further investigation we have been doing in this case led us to amend the complaint, which is not uncommon,” spokesman John Hall said outside court.

The Turpins were arrested on January 14 at their home in Perris, California, about 70 miles (113 km) east of Los Angeles, after an emaciated teenage girl climbed out of a window of the house and called police.

Officers responding to the scene found her 12 siblings ranging in age from two to 29 inside, suffering from malnourishment, muscle wasting and other signs of severe abuse.

Defense attorneys, who have asked the public to remember that their clients had a presumption of innocence, told the judge on Friday that they were skeptical they could be ready to proceed with a preliminary hearing in the case in May because of the voluminous amount of evidence turned over by prosecutors.

Both defendants are jailed in lieu of $12 million bail until trial and prohibited from contacting their children.

The children will not be required to testify during the preliminary hearing, at which a judge determines if there is enough evidence to bind the defendants over for trial, under a California law that allows police officers to summarize their testimony, sparing them further trauma.

The Turpins were ordered back to court on March 23 for another hearing in the case.