'The dark side took me away': BTK serial killer's daughter shares father’s letters from jail

The daughter of a US serial killer has shared letters exchanged between her and father as he sits behind bars.

In an interview with America’s ABC’s 20/20, which is airing today, Kerri Rawson reveals how she still has a strong bond with “the BTK killer” despite his crimes.

Between 1974 – 1991, Dennis Rader killed 10 people in the town of Wichita, Kansas.

“I wasn't corresponding with BTK. I'm talking to my father,” Ms Rawson told 20/20.

"I'm talking to the man that I lived with and loved for 26 years. I still love my dad today. I love the man that I knew. I don't know a psychopath. That's not the man I knew and loved." 

Her father’s identity wasn't known until 2005, when he sent a floppy disk to a local media outlet containing one of his infamous letters.

Over the years, BTK - standing for Rader's method of binding, torturing and killing his victims – was notorious for sending messages to police and the media.

This time, authorities traced the disk back to his church computer and he was arrested.

Rader was identified as a Cub Scout troop leader, church council president and father-of-two.

He was sentenced to 10 consecutive life sentences with a minimum of 175 years served.

"I had to learn how to grieve a man that was not dead, somebody I loved very much that no one else loved anymore," Rawson, who has written a book on her father, told 20/20.

Her book, titled A Serial Killer's Daughter, reveals other letters between the pair.

“You will always be my baby girl. I raised right-proud-independent and now is a grown adult with many years of love to give,” a letter read.

"Life before the arrest was a good time and the dark side took me away."

A Serial Killer’s Daughter will be available in Australia on Monday.