DNA, a Bloody Bat, and CODIS

12 Jun

In 1997 Susannah Chase was walking home from a pizza parlor in Boulder, Colorado. She never made it. She was found brutally murdered and raped, having been severely beaten with a baseball bat. She suffered at least four skull fractures, survived for a brief while, but ultimately succumbed to her injuries. A bloodied bat was found at the crime scene.


Flash forward to 2000 and a state away. Diego Olmos-Alcalde was arrested in Wyoming for kidnapping another woman. In 2001 he was convicted and sentenced to 10-20 years in prison. The Wyoming Supreme Court overturned that decision on a technicality and he was retried in 2004. He was again convicted and given a sentence of 7-10 years, with credit for time served.

Now back to Colorado where DNA from semen obtained from Susannah Chase was subjected to genetic evaluation by a company known as DNAPrint Genomics in Florida. They applied new techniques that allow some degree of racial discrimination from a DNA profile. Their determination was that the semen found in Chase came from a Hispanic or Native American.

Flash forward one more time to 2008 when Olmos-Alcalde’s DNA profile was entered into the Combined DNA Index System ( CODIS). There was a hit. Olmos-Alcalde’s DNA matched that of the semen sample taken from Susannah Chase. Olmos was arrested and now is on trial for the 1997 rape and murder of Chase.


A word about evidence: According to the Locard Exchange Principle, the heart and soul of forensic science, whenever an individual interacts with another person, place, or object there is an exchange of material. This may be simple hair and fiber, or maybe footprints, fingerprints, or tire tracks, or, as in this case, bodily fluids such as blood, saliva, or semen. But all the evidence does is create a link between an individual and another individual, place, or object. It is up to the courts to determine what this link means. This case is becoming a classic example of this type of evaluation.

The DNA evidence is as follows:

DNA from the semen found in Susannah Chase is that of Diego Olmos-Alcalde.

DNA found on the baseball bat, the murder weapon, matched the DNA of Olmos-Alcalde’s girlfriend and an unknown male. There was no DNA on the bat from Olmos-Alcalde.


How do we sort through all of this? Olmos-Alcalde admitted having sex with Susannah Chase but denied killing her. A wise move by either him or his attorneys, since the DNA absolutely connected him to the victim and if he denied knowing her or ever having been near her, he would have a problem. So the DNA findings do not dispute his story. The mere finding of his semen in the victim does not mean that he raped or murdered her only that sexual intercourse took place. It does connect him with the victim but that’s all it does.

But what of finding DNA from Olmos-Alcalde’s girlfriend on the bat? Witnesses said that she owned a bat similar to the murder weapon and her DNA connects her to the bat used to kill Chase. And since she and Olmos-Alcalde had a relationship, he had access to this particular bat.

The finding of DNA from an unknown male on the murder weapon is problematic for the prosecution. Is this DNA simply from someone the girlfriend knew, someone who had been in her home and handled the bat, in which case it is a classic red herring. Or is it the DNA of someone unknown to her and Olmos-Alcalde? Someone who could be the real murderer. Olmos-Alcalde could have had sex with Chase, left her to walk home on her own, where she encountered another male who committed the murder.

Evidence, besides making a connection, can also be additive and cumulative, meaning that the more evidence that piles up the worse it looks for the defendant. In this case, Olmos-Alcalde cannot and does not deny that he had contact with Susannah Chase. His DNA makes that clear. His defense will obviously be that the unknown male killed her after he had had innocent sex with her.

But does this seem plausible? What are the odds that an unknown male stole the murder weapon from the girlfriend’s home and used it to kill a young woman that Olmos-Alcalde had just had sex with? Would that even work in fiction? Maybe, if you’re writing a story where someone is framed, but logic is against this actually happening. What are the odds? Lottery ticket odds, particularly since the police questioned more than 500 people and took DNA and hair samples from 30 men, including a homeless man found in the alley near the crime scene. Further complicating the picture, this unknown male DNA could have been on the bat for months, even years if the bat were not used or cleaned in any way.

The DNA connects Olmos-Alcalde directly to the victim and indirectly to the murder weapon. Now the jury must decide what these connections mean. This will be an interesting case to follow as it unfolds.

Rocky Mountain News Story



Posted by on June 12, 2009 in DNA, Interesting Cases


16 responses to “DNA, a Bloody Bat, and CODIS

  1. Craig Faustus Buck

    June 12, 2009 at 7:47 pm

    Doug, I think you missed the boat on this one. There are several plausible scenarios that pop to mind that could explain this situation without implicating Olmos-Alcalde.

    1. He had sex with the victim and his gf, who owns the bat, got angry and killed her.

    2. The “unknown male” was involved with the girlfriend and saw an opportunity to frame Olmos-Alcalde by killing the woman with his girlfriend’s bat while the victim had Olmos-Alcalde’s DNA in her.

    3. The “unknown male” was a relative of the girlfriend who grabbed his relative’s bat to kill the girl who was enticing the girlfriend’s lover to cheat.

    4. The “unknown male” was a friend of Olmos-Alcalde and/or his girfriend and the victim was his girlfriend. When Olmos-Alcalde had sex with her, the friend became enraged, grabbed the girfriend’s bat and killed the victim.

    Just because the male is “unknown” to the police does not mean he is unknown to the owner of the bat, to Olmos-Alcalde or to the victim.

    Am I wrong?


    • D.P. Lyle, MD

      June 12, 2009 at 9:08 pm

      Thank you, thank you. This is exactly what I hoped this blog would be. A place where I could talk about a forensic issue surrounding a relevant case and have writers take those thoughts and the linked stories and say “What if?” This blog is for writers. We get our stories from newspapers, TV, life, etc. This case was one that made me, like you, think–What if? I love the plots you laid out. I have several in my head too, several of which could make a pretty good story.

      The twist in this case was the girlfriend’s DNA on the bat and the fact that this could link the bat back to the suspect. Or not. In this case, because of what the police did and the history of the suspect, I think the evidence and linkages are more straight forward than we mystery writers like. And I tried to stay true to the case. But the plot lines you came up with—and I hope other readers of the blog did too–though not likely true here, are great stories and storytelling is what I hope comes out of this entire project. I think the other cases I’ve posted since starting this blog–the child’s body in the sandbox, the baby stolen from the mother’s womb, and the sad, sad situation with David Carradine—will also cause this type os What if? moment in everyone who visits here. That’s the hope anyway.

      Again thanks for your comments and please keep them coming. Let’s have a free for all of ideas.


  2. Craig Faustus Buck

    June 12, 2009 at 10:41 pm

    Thanks, Doug. I love your blog.


  3. Kenna

    June 13, 2009 at 6:00 am

    Doug – Your posts do get the creative juices flowing and the possibilities are wide open – epecially if we allow for creative license. Fleshing out means, motive and opportunity are what lead to a great story; wel that and a canny and flawed sleuth 😉

    I really enjoy your blog. Thanks for the inspiration!


    • D.P. Lyle, MD

      June 13, 2009 at 8:38 am

      Thanks. That’s the goal. I’m glad you find the blog interesting and plot provoking.


  4. Bill S.

    June 13, 2009 at 10:04 am

    Doug – this is really good stuff. Thanks for taking the time. See you at Thriller Fest.


  5. Joe Chile

    January 15, 2010 at 10:29 am

    This guy was convicted right? What did he get? Life, Years??


    • D.P. Lyle, MD

      January 16, 2010 at 11:59 am

      Not sure. I think the case is still in progress.


  6. clyde

    December 15, 2011 at 10:22 pm

    Hi other kidnapping and violent sexual attacks make him even more likely than “an unknown male”
    Geez… when a baseball bat is at a game several people may use it.

    Of course he did it..


  7. milos

    May 13, 2012 at 8:44 pm

    FYI, he was convicted on all charges in June 2009. I was on the jury and recently decided to read up on anything that happened after the case, which is how I found this blog. Just looking at the DNA evidence might sound conflicting or open up a wide range of possible situations… but when all the evidence came together there was no reasonable doubt.


  8. Cristina

    July 27, 2013 at 7:10 am

    I think alcalde Washington framed! An easy target… It’s impossible to me, or at least extremely suspicious that there’s semen of Alcalde but no DNA on the bat that supposedly he used to strike and kill her. If he would of been clever enough to clean the bat, then there would of been no DNA found of the girlfriend or another male. Also if ever that bat would of been held by alcalde in the past, even to put inhis car, the his DNA would of been on it! He was framed! & the detectives didn’t do their job.


    • D.P. Lyle, MD

      July 27, 2013 at 10:04 am

      Maybe, maybe not. We’ll see.


    • alice

      October 5, 2013 at 5:58 pm

      The absence of alcalde’s dna could simply mean he wore gloves. This crime seems to be premeditated and not a crime of opportunity. The bat was brought to the crime scene. Its not a stretch to assume the perp thought of gloves as well. I would like to know how alcalde claims he and chase first became acquainted. He claims that he and the victim had consensual sex. Under what circumstances?


  9. Jess

    June 10, 2014 at 4:58 pm

    If he wore gloves why didnt he wear a condom????


    • D.P. Lyle, MD

      June 10, 2014 at 7:58 pm

      Stupid is as stupid does–or maybe he had sex with the victim but someone else was the killer. Or maybe he wiped down the bat, knowing about fingerprints, but didn’t understand DNA. Probably missed that episode of Forensic Files.


  10. Jacob Bryan

    October 4, 2016 at 11:33 am

    Did anybody ask him were he was when jonbenet got killed.



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