New details on a catastrophic criminal mix-up. The DNA of thousands of convicted felons is not in the system.

The stunning allegations came Wednesday from the state's top cop. Attorney General J.B. Van Hollen says not only did an alleged serial killer pull a fast one, but 12,000 other criminals in prisons have yet provide a DNA sample as required by law.

It's the job of the Department of Corrections and some sheriff's departments to collect DNA samples and send them to the state crime lab.

The crime lab is part of the Department of Justice.

It was a mistake discovered while investigating the north side strangler case led to the discovery.

DNA will be critical in the case against accused north side strangler Walter Ellis. Now we are learning the DNA sample Ellis supposedly gave while in prison was someone else's.

"We have reason to believe that Walter Ellis convinced another inmate to give a DNA sample and an accompanying fingerprint of the other inmate because he did not want to give a sample for reasons I think we can now appreciate," said Van Hollen.

The Department of Corrections claimed they sent Ellis' DNA sample to the state crime lab back in 2001.

At the time, the crime lab found that the DNA sent wasn't Ellis' but they never notified the Department of Corrections to get another sample.
 
Van Hollen said they know which inmate offered up his DNA to help Ellis and he'll be referred to the Milwaukee County District Attorney's office for review.

If Ellis' DNA had been in the system, it might have allowed police to connect Ellis to multiple murders sooner.

Ouithrean Stokes was killed six years after the DNA switch.

"If that young woman would have been from Whitefish Bay it would not have been an issue of could we find the DNA," said Milwaukee defense lawyer Robin Shellow.

She isn't involved in the Ellis case but she has been an outspoken critic of the state's justice system.
 
"Corrections' has egg all over its face," said Shellow, "So it's easiest to blame the serial murder suspect isn't it?"

The Department of Corrections says it has taken thousands and thousands of DNA samples from prisoners, but it's looking into its procedures including if Ellis gamed the system.

The Attorney General wants to know too.

"So that we don't have more people like Walter Ellis who managed to find a way to slip through the cracks in the future," said Van Hollen.