The researcher, who has only been identified by his surname, Lee, was based at a microbiology research centre in Ganggye, close to the Chinese border.
However, according to a group that campaigns for human rights in North Korea, he fled to Finland on 6th June.
He allegedly has an electronic data storage device that contains evidence proving that North Korea have been testing biological and chemical weapons on humans.
The 47-year-old is planning to give testimony to the European parliament in late July in order to highlight the North's abuses of its own people, the rights group said.
Daniel Pinkston, of The International Crisis Group in Seoul, said action should be taken against Kim.
He said: “If it can be verified that such experiments have taken place, then that would seem to violate international humanitarian law.
“After that, it is up to the international community to do everything in its power to prevent this happening again, to terminate these programmes and to hold those responsible for carrying them out accountable.”
It is not the first time it has been claimed that North Korea have tested chemical weapons on humans.
Im Cheon-yong, who fled his role as an officer in Noeth Korea’s special forces, also claimed that mentally and physically disabled children being used in chemical weapons tests as part of his training.
“For the biological and chemical warfare tests, we needed ‘objects’,” he said in an interview last year.
“At first, they used the chemical agents on mice and showed us how they died. Then we watched the instructors carrying out the tests on humans to show us how a person dies.
"I saw it with my own eyes.”
It is not yet known what action will be taken against Kim Jong Un if these testimonials prove to be true.