What is Y-STR DNA Testing?

Since it was first used for a criminal case in 1986, DNA testing has been an essential tool for forensic investigators in solving current and cold cases. If you've watched even one episode of one of the CSI shows or are a true crime junkie, then you know that DNA testing is crucial to proving someone's guilt - or innocence.

DNA can place a suspect at a crime scene or, if you're a forensic genealogist, help solve cases that went cold decades ago. They can even help identify the remains of those long deceased, which is the case in the recent identification of Edith Patten, a 24-year-old woman who died in 1891 from tuberculosis and whose identity was essentially lost to history until historians and the DNA Doe Project were able to identify Edith.

DNA evidence became more common in criminal trials, but now it can be found in other settings, including in labs where cancer-curing research is being conducted. And, of course, you can simply swab the inside of your mouth and send it to 23andme to learn about your health risks, pharmacogenetics, and carrier status, not to mention finding blood relatives who have also submitted DNA samples.

So, how is Y-STR DNA testing different? What makes it so effective for use in cold cases and sexual assault cases? Is it all that accurate, and what are its limitations?

Buckle up, my true crime buttercups! We're about to delve into the history of DNA testing and how useful Y-STR testing can be in certain cases.

A History of DNA Testing

In the 1860s, a Swiss chemist named Friedrich Miescher identified DNA. He isolated what he called 'nuclein' and identified DNA as a distinct molecule. However, it was not until 1953 when biologist James Watson and physicist Francis Crick described DNA as existing in the form of a 3D double-helix. Thanks to Watson and Crick, DNA research massively amped up.

Paternity cases started utilizing DNA testing in the 1980s before, in 1986, a clever young geneticist by the name of Alec Jeffreys was brought onto a murder case to work with investigators. Two years prior, Jeffreys developed DNA fingerprinting.

Investigators were trying to find out who has murdered two 15-year-old girls (after sexually assaulting them) in Leicestershire, England. A 17-year-old boy with learning difficulties stood accused, and the police hoped Jeffreys would be able to prove the boy had killed both girls. However, Jeffreys did just the opposite, ruling the young man out as a suspect.

Leads were quickly drying up, and police knew they needed to act fast. Jeffreys decided to create genetic profiles of males in the area. In the meantime, a local banker named Colin Pitchfork was reported to have bragged about how he had submitted his buddy's DNA instead of his own. Police were alerted and decided to bring Pitchfork in for questioning. They got Pitchfork's real DNA, and Jeffreys matched it to the profile he had created.

While this prompted the development of forensic DNA analysis, it was debatable whether DNA testing results should be admissible in court. There were many legal and ethical issues surrounding the retrieval of DNA from suspected criminals, and that meant rigorous legal procedures had to be established. Today, obtainment and chain-of-custody are highly regulated, and one little misstep by anyone involved in an investigation could throw a trial into chaos.

The Rise of Crime Shows and Ending the Backlog of Untested Rape Kits

I'm not gonna lie, I absolutely love the CSI shows, especially the original. The early aughts brought us a slew of crime dramas of this ilk, from NCIS to Criminal Minds. A lot of forensic investigative techniques are highlighted in these shows, but what viewers still tend to misconceive is that forensic results can happen in one or two days.

That just isn't the case. Not in the slightest.

Just ask Mariska Hargitay, star of Law & Order: SVU. Hargitay's character, Olivia, investigates sexual crimes, and this role seems to have deeply impassioned Hargitay. She is an amazing advocate who works with the Joyful Heart Foundation on End The Backlog, an effort to reform and pass intensive legislation in all 50 states to ensure that no rape kit sits on a shelf collecting dust.

As the Joyful Heart Foundation states on the ETB website:

"[t]he backlog of untested rape kits represents the failure of the criminal justice system to take sexual assault seriously, prioritize the testing of rape kits, protect survivors, and hold offenders accountable. There are several key contributing factors that create a backlog."

There is a clear lack of protocols and policies in place for testing these kits, a lack of training and gaps in knowledge and understanding as to how sexual assault and rape create trauma in people's lives, and a potentiality for a perpetrator to be a repeat offender and not yet caught. Furthermore, lab policies might be antiquated and resources unavailable due to loss of funding and lack of personnel in public crime labs throughout the country.

Joyful Heart has been working since 2010 to end the backlog. Their objectives are:

1. To implement an annual statewide inventory of kits.
2. Mandate the submission and testing of all backlogged kits.
3. Mandate the testing of all new kits.
4. Create and use a statewide kit tracking system.
5. Implement mechanisms for survivors to easily find out about the status of their kits.
6. Allocate appropriate funding to submit, test, and track kits.

These Six Pillars were developed in 2016 and give the US a "standardized way to understand and analyze the severity of the backlog problem."

You see, the truth is, we have the technology to test these kits and identify sexual predators. But it isn't being done for a multitude of reasons. Unfortunately, this only creates more victims and a bigger backlog of untested kits. At least we have Joyful Heart and Hargitay out there pushing for such necessary reform and funding for testing resources.

What is Y-STR Testing?

Y-STR DNA testing is part and partial to testing in both sexual assault and cold murder cases. Y-STR is Y-chromosomal testing that detects foreign male DNA on a victim, serving as an alternative to the standard autosomal short tandem repeat (A-STR) testing proves unhelpful in an investigation. Male DNA can get masked by or in competition with excess female DNA, so, at best, you might only get a partial DNA profile for the male DNA.

Y-STR testing specifically targets STR regions on the male Y chromosome passed down from father to son. This means that, even when there is female DNA present, a stable profile can be built for the male DNA being tested. There have even been cases in which Y-STR profiles were constructed without sperm or seminal fluid detected by serology and when male DNA is very low or below the detection threshold.

This provides hope for solving cases that went cold long ago. For the families and friends of murder victims, even a sliver of hope is something to cling to. For them, closure never comes, but getting a violent offender off the street is another step in the grieving and healing process.

The Benefits of Y-STR Testing

What exactly are the benefits of Y-STR DNA testing? There are quite a few to consider:

1. Assisting in excluding suspects
2. Male-to-male mixtures can be resolved
3. A number of male donors in a mixed sample can be determined
4. Inconclusive STR results can be resolved
5. Male-only DNA in mixed samples can be targeted
6. Male DNA can be detected in cases involving:

• Lengthy periods of time between collection and testing
• No ejaculation occurred
• Males were vasectomied or azoospermic
• Digital penetration
• Saliva that occurred after showering
• Sperm degradation from improperly stored or backlogged rape kits

Why Y-STR is Helpful in Sexual Assault Cases

Now that there is such a huge push to end rape kit backlogs, Y-STR testing can effectively test DNA samples in which degradation occurred. This has long been a limitation with standard STR testing, so as the testing of rape kits speeds up, Y-STR can help workflow.

Y-STR profiles can be developed around six days post-coital, and they might even be able to push the boundaries further, hitting a nine-day post-coital benchmark.

Why Y-STR is Helpful in Cold Cases

As I already hit upon, Y-STR is also helpful in tackling long-gone-cold cases. The National Institute of Justice (NIJ) has been funding Y-STR testing for quite a while now since it is so promising. As Philip Bulman writes, testing Y-STRs in the case of 19-year-old Mary Sullivan - who was raped and murdered just days after her move to Boston in January of 1964 - proved to be massively beneficial at getting answers.

As the results revealed, Mary was one of the 11 victims of the Boston Strangler (Albert DeSalvo). Although DeSalvo was sentenced for other rape charges and died in prison in 1973 when stabbed to death by other inmates, there was no concrete evidence to prove he was Mary's killer.

When Y-STR DNA testing was done in 2013, 99.9% of other males were excluded from the profile, meaning that DeSalvo had indeed raped and strangled Mary. The only reason it is not 100% is that other male family members cannot be fully excluded.

With this data in hand, Boston investigators went and exhumed DeSalvo's body in July of 2013 so that a confirmatory test could be performed. The results? The odds of another white male being the DNA donor were one in 220 billion. This gave investigators all the proof they needed.

Potential Disadvantages

Y-STR testing has some limitations, and those come in the form of its inheritance pattern and haploid nature. Those limitations are being reduced as technology enhances Y-STR testing. While establishing patrilineal lines is helpful in cold cases or trying to find missing persons in the aftermath of massive disasters, criminal investigations will benefit from even further relative distinctions.

Another Example

DNA testing really has come a long way, and here is where I cite a case that happened in my hometown of Grand Rapids, Michigan. In November of 1999, a 26-year-old woman was raped in a parking lot. She had just left a night class at Kendall College of Art and Design and was walking toward her car. She was raped from behind and was therefore unable to provide police with a description of her rapist. What's more, the rapist left no fingerprints, and nobody else was around to witness the event. The case seemed like a lost cause.

However, five years later, a parole application for a man doing time for another sexual charge mandated his DNA sample. When it was popped into CODIS, it showed he was a match to the sample collected from the 1999 rape case in GR.

So, what was the catch?

The convict was a twin - an identical twin. Standard STR testing does not differentiate between identical twins' DNA. This meant that prosecutors could not press charges against either twin. The case remained open.

Since then, though, there have been many advances in DNA sequencing. But there are some legal issues that have been stalling this particular case. In 2018, Kent County Prosecutor Chris Becker vented his frustrations after a Boston judge ruled that this type of DNA testing technology was inadmissible in court despite Jerome Cooper of Twin Lakes having been identified as the suspect via standard DNA testing. But could his twin, Tyrone, have been the rapist?

Both men, now in their 50s, have raps for sexual assault. Both men deny being the rapist and were unable to provide alibis.

Kent County prosecutors got massively excited when a new sequencing technology established in Europe could differentiate mutations between identical twins. Unfortunately, the test costs over $100,000.

A similar case in Boston (whoa, Boston again...) in 2012 used this technology, but a Boston judge ruled it inadmissible in court since it had not been independently verified by scientists. This put a major delay on the Grand Rapids case. As of writing this in March of 2023, I have not heard any further updates on the case. The idea of either Cooper twin still being out there among the general public unnerves me, to say the least.

This Crime Writer Chick's Verdict

DNA testing technology has been around for decades now, but we still have a long way to go. There are so many backlogged rape kits, so many unsolved cold cases, so many perpetrators still out there, so many people still wondering who took their loved ones away from them forever.

We need to keep enhancing technology so that answers can be obtained. Y-STR testing shows how far we've come, and its benefits outweigh its limitations.

Technology can work for us, but we have to work to ensure that the courts see the benefits of new forms of enhanced DNA testing.