By Sara Murray and Jason Morris, CNN

Updated 2:43 AM ET, Wed March 17, 2021

The Atlanta-area district attorney investigating former President Donald Trump, Fani Willis, is beefing up her office with a new evidence expert, according to a source familiar with the situation.

Michael Carlson, known as an expert in the rules of evidence, is slated to join the Fulton County District Attorney's Office in the coming weeks. He's expected to work on a variety of issues, from cold cases to capital murder to public integrity investigations.

While Carlson was not hired explicitly to work on the probe into Trump, his expertise on the rules of evidence and criminal procedure is sure to be seen as a valuable addition for an office investigating a former President.

Carlson recently worked as the director of legal services and ethics officer for the Georgia Bureau of Investigation. He is the co-author of "Carlson on Evidence" -- a book he wrote with his father, University of Georgia law professor Ronald Carlson -- which offers a detailed comparison between Georgia and federal rules on evidence.

Carlson did not immediately respond to a request for comment.

His hiring comes weeks after Willis hired John Floyd, a nationally renowned lawyer known for his deep expertise in racketeering cases. Floyd is expected to assist the district attorney's office on multiple cases in the white-collar, gang and public corruption units, Jeff DiSantis, a spokesman for Willis, told CNN.

Two people familiar with Floyd's hiring told CNN that he was not retained specifically for the investigation into Trump's post-election call with Georgia Secretary of State Brad Raffensperger.

"He was retained for his racketeering expertise generally -- not for any specific case," said DiSantis.

Unlike Floyd, who is contracted to work only part time for Willis' office, Carlson is being brought into the district attorney's office full time as a staff employee.

Willis opened a criminal investigation into Trump for his "attempts to influence the administration of the 2020 Georgia general election."

In a letter to numerous Georgia state election officials, including Raffensperger, Willis requested that they preserve documents related to Trump's January phone call in which he pushed Raffensperger to "find" votes to reverse his election loss.

Raffensperger's office also launched its own probe into Trump's attempts to overturn the election, an inquiry that includes a review of both that call and another phone call the then-President made to a Georgia election official.