In an unusually written motion, federal prosecutors had strong words for a young woman accused of torturing, murdering and mutilating an Albuquerque man. 

The feds are arguing to keep 19-year-old Mariah Ferry behind bars until her trial. 

She and her boyfriend, Chase Smothermon, are accused in the kidnap and murder of John Soyka over a drug debt. 

In the motion, prosecutors point to video the couple took of the crime, where Ferry is giggling at times as she uses a hatchet on the body. 

(Warning: The motion contains details some might find disturbing) 

Read the motion here >> 

They argue she’ll appear to the court as a soft-spoken, young-looking girl with no criminal record, but “she possesses a darkness that forms the basis of her true history and characteristics.” 

The document elaborates on the torture and mutilation, saying the young woman used a hatchet in the murder, then helped carve up the body and sever the victim’s genitals while taking pictures and videos of it all.