In October, the city of Philadelphia, Pennsylvania, issued an apology. It’s an apology half a century overdue, for a heartbreaking case of discrimination and injustice.

From the 1950s to the 1970s, Holmesburg Prison conducted unethical medical experiments on its inmates. The experiments were performed mostly on black men.

Dr. Albert Kligman was a dermatologist. He’s best known for inventing Retin-A, a treatment for wrinkles and acne. He first visited Holmesburg Prison to help cure an outbreak of athlete’s foot. While there, he got an idea.

When he looked at the inmates of Holmesburg Prison, he didn’t see human beings made in the image of God. He saw subjects for experiments. As he told one newspaper, he saw nothing but “acres of skin.”

The inmates agreed to the experiments, but they didn’t know what would happen. Many still awaited trial, saving money for bail in the meantime. They were promised the experiments wouldn’t be hazardous.

Dr. Kligman exposed about 300 inmates to viruses, fungi, and asbestos. He exposed some of them to dioxin, a toxin that can cause cancer and birth defects. Some inmates received burns and permanent scars from the experiments. Many would suffer health problems for the rest of their lives.

In 2000, a group of the inmates sued Dr. Kligman and his university. But the statute of limitations (the amount of time you have to take legal action after someone wrongs you) had run out. The court wouldn’t hear the case.

Last year, the University of Pennsylvania—where Dr. Kligman worked—issued a formal apology. University officials removed Dr. Kligman’s name from current programs. The university also gave money to fund research into skin issues among people of color.

Now Philadelphia’s mayor, Jim Kenney, has also publicly apologized.

“Without excuse, we formally and officially extend a sincere apology to those who were subjected to this inhumane and horrific abuse,” says Kenney. “We are also sorry it took far too long to hear these words.”

To some of the victims’ families, an apology isn’t enough. They want to see real justice done.

God values all human life. It’s a grievous thing to treat others as less than human because of their skin color, or even because they’ve committed crimes. Prisoners still have human rights. The law is meant to protect, but sometimes it fails.

True repentance takes more than words. It takes action—turning away from the wrong. But an apology is a good place to start.

Why? All people are made in the image of God and have dignity, no matter what they look like or what they’ve done. Fallen humans too often forget that and act on impulses shaped by errant desires.