Hess and Koch used their funeral home to steal bodies and body parts at times, using fraudulent and forged donor forms.
A former funeral home owner in Colorado, United States, Megan Hess, has bagged 20-year jail terms after admitting to have defrauded relatives of the dead by dissecting 560 corpses and selling body parts without permission.
In July, Hess, 46, pleaded guilty to fraud. From the same building in Montrose, Colorado, she ran a funeral home, Sunset Mesa, and a body parts company, Donor Services. The maximum allowed by law was a 20-year sentence.
Hess and Koch used their funeral home to steal bodies and body parts at times, using fraudulent and forged donor forms.
According to prosecutor Tim Neff said in a court filing, "Hess and Koch's conduct caused immense emotional pain for the families and next of kin."
A 2016-2018 Reuters investigative series about the sale of body parts in the United States, a virtually unregulated industry, prompted the federal case.
Former employees told Reuters that Hess and Koch performed unauthorised body dismemberments, and the FBI raided the business a few weeks after a 2018 story was published.
In their filing, prosecutors stressed the "macabre nature" of Hess' scheme and described it as one of the most significant body parts cases in recent U.S. history
"This is the most emotionally draining case I have ever experienced on the bench," U.S. District Judge Christine M. Arguello said during Tuesday's sentencing hearing in Grand Junction, Colorado.
"It's concerning to the court that defendant Hess refuses to assume any responsibility for her conduct."
The judge ordered that Hess and Koch be sent to prison immediately.
Hess' lawyer said she has been unfairly vilified as a "witch," a "monster" and a "ghoul," when instead she is a "broken human being" whose conduct can be attributed to a traumatic brain injury at age 18. In court on Tuesday, Hess declined to speak to the judge.
Koch told the judge she was sorry and took responsibility for her actions.
Twenty-six victims described their horror at discovering what had happened to their loved ones.
"Our sweet mother, they dismembered her," Erin Smith said, selling her shoulders, knees and feet for profit. "We don't even have a name for a crime this heinous."
Tina Shanon, whose mother was dismembered against her will, told the court, "I've worn many masks to cover the pain. I'll never be OK."
Organs such as hearts, kidneys, and tendons cannot be sold in the United States; they must be donated. However, selling body parts such as heads, arms, and spines for use in research or education, as Hess did, is not regulated by federal law.
Prosecutors charged Hess with crimes when she defrauded relatives of the deceased by lying about cremations and dissecting and selling bodies without permission. Prosecutors claimed that the surgical-training companies and other firms that purchased the arms, legs, heads, and torsos from Hess had no idea they had been obtained fraudulently.
Prosecutors said Hess charged families up to $1,000 for cremations that never happened at her funeral home, and she offered others free cremations in exchange for a body donation.
Prosecutors claimed she lied to over 200 families who received cremated ashes from bins containing the remains of various cadavers.