STRmix™ Plays Key Role in Linking Serial Killer Ted Bundy to 52-Year-Old Cold Case

PG Software Helps to Identify Bundy DNA in Decades-Old Sample

STRmix™ has played a key role in closing a 52-year-old cold case, attributing the 1974 murder of 17-year-old Melissa Ann Smith to infamous serial killer Ted Bundy.

STRmix™ is a software tool used by more than 100 case-working laboratories within the U.S. to resolve mixed DNA profiles previously regarded as too complex or degraded to interpret crime scene evidence.

Using STRmix™ and Short Tandem Repeat (STR) genotyping technology, the Utah Bureau of Forensic Services was able to connect the Smith case to a second decades-old murder in the state which had previously been linked to Bundy. Earlier this year, DNA found in that case connected Bundy to the murder of another 17-year-old, Laura Ann Aime. Aime’s body was found just a few weeks after the body of Smith was discovered in 1974.

Before his execution in 1989, Bundy admitted to killing Aime. It was not until earlier this year, though, that Utah investigators linked Bundy to a degraded DNA sample found at the Aime crime scene using STRmix™.

From there, investigators were able to use the new evidence from the Aime case to reexamine the Smith case. Using STRmix™ and STR genotyping technology, forensic scientists were able to connect the two cases to each other and to Bundy. Y-STR testing, which analyzes repeating DNA sequences on the male Y chromosome, further supported that Smith, like Aime, was a victim of Bundy.  

Since its introduction in 2012, STRmix™ has proven to be a highly effective tool in producing usable, interpretable, and admissible DNA results in more than 700,000 criminal cases worldwide. It has been particularly effective in helping to resolve violent crime and sexual assault cases, as well as cold cases in which evidence was originally dismissed as inconclusive.

“The popularity of STRmix™ is due in no small measure to its ability to interpret DNA results faster than our old manual methods and use more of the information in a DNA profile,” explains STRmix™ co-developer Dr. Jo-Anne Bright, a Senior Science Leader within the STRmix team at the New Zealand Institute for Public Health and Forensic Science Limited (PHF Science).

Unlike previous methods of DNA analysis, which depended entirely on the application of fixed thresholds to manually analyze DNA samples, STRmix™ uses probabilistic modelling to evaluate all available DNA evidence and objectively assesses the likelihood of different contributor combinations. 

The worldwide success of STRmix™ has led the team behind its development to create and regularly update three related software applications:  

• FaSTR™ DNA, expert forensic software which seamlessly integrates with STRmix™ (when in use) to rapidly analyze raw DNA data and assign a NoC estimate; 
• DBLR™, an application which when used with STRmix™ allows forensic laboratories to undertake extensive kinship analysis, carry out rapid database searches and mixture-to-mixture matches, and visualize the value of their DNA mixture evidence; 
• STRmix™ NGS, fully continuous mixture interpretation and LR generation software for profiles generated using Next Generation Sequencing. 

In combination with STRmix™, FaSTR™ DNA and DBLR™ complete the full workflow(external link) from analysis to interpretation and database matching, while STRmix™ NGS broadens the range of profile types that can be interpreted.

STRmix Limited is a wholly owned subsidiary of PHF Science, a New Zealand government research organization. STRmix Limited was founded to better serve international users of STRmix™ software. 

STRmix – A global leader in forensic DNA interpretation, trusted by more than 130 forensic laboratories worldwide.