Jupiter was at a loss for answers in the days and months after the 2017 Super Bowl: Three people in their 20s had been fatally shot in the backyard of a home in a town where homicides are rare. But eventually, technology that fewer than 100 forensic labs nationwide are trained to use helped uncover some of the answers, authorities say.
Two men — Christopher Vasata and Marcus Steward — are in custody and charged with three counts of first-degree murder. They were arrested eight months apart, and the second of those arrests – which came nearly 10 months after the slayings – was made possible in part by STRmix, a software program that the Palm Beach County Sheriff’s Office Forensic Biology Unit began using in August.
STRmix uses an algorithm to help scientists identify individual DNA contributors in evidence that contains several people’s DNA. That program helped decipher key pieces of evidence that led to the November arrest of Steward, long after Vasata’s arrest in March.
Celynda Sowards, a senior forensic scientist with the sheriff’s office, said the technology is enhancing the way scientists help authorities in criminal cases.
“In the old days you would have a road atlas, and that’s how you got from point A to point B. Now, you have all different kinds of apps help you get there,” Sowards told The Post Thursday. “So the road atlas that got you there still works, but now there’s just more information that you can use to get you there.”
On Feb. 5, Kelli J. Doherty, 20, of Tequesta; Sean P. Henry, 25, of Jupiter; and Brandi El-Salhy, 24, of Gainesville were shot and killed in the backyard of a home on Mohawk Street in the Jupiter River Estates neighborhood, south of Indiantown Road and west of Military Trail.
Charles Vorpagel, who rented the home, escaped the shooting scene uninjured. He told police that at least three people in masks and gloves entered the backyard shortly after 10:30 p.m. and said, “Pay what you owe, (expletive).”
Police reports later indicated drugs were at the center of the shooting.
Vorpagel also said Henry’s car was missing from the driveway. A few hours later, the Honda was found abandoned on Interstate 95 near Northlake Boulevard in Palm Beach Gardens. A rifle, some bloodied items, gloves and clothing were found in and near the car, according to Jupiter police.
Vasata, who was injured in the shooting that night, was found dumped in front of a BMW on a street in Paseos, a neighborhood a few streets south of Mohawk. He was arrested March 20 when he was released from a hospital.
Vorpagel was arrested on unrelated federal guns and drugs charges. On Nov. 29, Vorpagel pleaded guilty to the charges, and is set to be sentenced Feb. 16.
The fatal shootings stunned residents in Jupiter River Estates, a quiet neighborhood near Jupiter Christian School, and the town on a whole. Before the triple homicide on Feb. 5, the last homicide in Jupiter was in 2015. In total, there have been only 11 homicides in the town since 2009, according to a Palm Beach Post online database.
Steward, who most recently lived in suburban West Palm Beach, was a suspect from the beginning because his cellphones were found in the back of the BMW that Vasata was dumped in front of. Steward told police he had forgotten them in the BMW when Vasata sold him marijuana earlier in the evening. It wasn’t until further DNA analysis was done on the items in the stolen Honda, however, that Steward was arrested on Nov. 28.
Called a genetic blueprint, deoxyribonucleic acid — or DNA — is the individual molecular code inside every organism. It carries biological information from one generation to the next and provides instructions on how to develop, survive and reproduce. And it’s in every cell in our bodies including blood and sweat.
The four factors
Celynda Sowards, a senior forensic scientist with the Palm Beach County Sheriff’s Office, said that in order for analysts to look at the DNA from evidence in a criminal case, they must deal with four factors:
Extraction: Getting the DNA and leaving everything else out.
Quantification: Figuring out how much DNA is obtained. Is it an adequate sample?
Amplification: Looking for distinct characteristics in 24 specific areas of the DNA, or markers that are used to identify individuals.
Visualization: Looking at the profile in the end.
The first person in the United States to be convicted of a crime using DNA evidence was Tommie Lee Andres in Orange County, Florida, in 1987 for rape. Since then, DNA has been used both to convict and exonerate hundreds of people across the U.S.
Even with the incredible leap in technology and science, PBSO Forensic Biology Unit Manager Julie Sikorsky said DNA isn’t necessarily “a silver bullet” for every crime.
“Just because your DNA is found in this room and a homicide is committed later in this room today, that doesn’t mean you did it,” Sikorsky said. “(Analysts) help (law enforcement) interpret the context of the DNA. But we stay away from the guilty/innocent part.”
Sowards, the forensic scientist, said on the screen, DNA looks like peaks on a heart-rate monitor. When analysts get evidence with single contributors, or only one DNA profile, those results tend to be more straightforward: a single set of discernible peaks.
When there is more than one person’s DNA in a sample, more peaks show up and they become harder to differentiate. She said that’s why in cases like rape or stolen vehicles, victims are often asked to provide their DNA so they can be ruled out when investigators look at the profiles.
But not all mixtures have simple eliminations. Sikorsky said that as DNA detection methods became more sensitive over the years, analysts were able to pick up more information with smaller samples. Because of that sensitivity, more DNA mixtures appeared in the readings.
“So there’s a lot more we were detecting, which can be very helpful in determining who was at a crime scene or interactions with some items of evidence,” Sikorsky said.
Inside Sean Henry’s stolen Honda, as well as outside on the side of the roadway, were a bloodstained pillow, black gloves, a T-shirt, a black hooded sweatshirt and other items covered in blood and sweat. Vasata’s DNA was found in one of the gloves. The keys to the BMW also were found near Henry’s car.
The issue, according to a Jupiter police report, is that the DNA samples on those items were mixed and could not be discerned by the technology at the sheriff’s office at that time.
The new technology
STRmix’s algorithm helps forensic scientists interpret complex DNA samples through a process called probabilistic genotyping.
Though scientists can interpret the DNA mixtures as three or four people, they may not be able to say which piece of DNA came from which person. That’s where STRmix comes in: Analysts put the data from the complex mixtures into the software and the computer separates them into their own parts.
With the information, STRmix runs at least 500,000 iterations to explain the data in minutes to hours, depending on how complex the sample is. Sowards said it works like the board game Battleship: Players guess certain coordinates on an opponent’s board trying to figure out where a battleship is placed. The program makes guesses until it gets a “hit” in the sample. Each guess is given a certain weight based on how accurately it explains the DNA mixture.
Sowards said instructors at STRmix showed them the calculations the software uses to come up with each of the probabilities. She said it would “take a year” for each analyst to do it manually for each case.
As of November 2017, there were 29 labs in the United States that use the STRmix technology — including the Florida Department of Law Enforcement and the FBI — and another 51 labs were being trained.
Sikorsky said the sheriff’s office began training with the technology in July 2016. Between a National Institute of Justice grant and PBSO funding, it cost $230,000 for seven software licenses, validation of the software and training.
After the technology went into use in August, the sheriff’s office started checking cases, old and new, right away. Not all cases are eligible to be tested: Analysts must know how many people make up the DNA mixture. As of now, about two-thirds of all DNA cases are put through the software, Sikorsky said.
“The very first week we were online, we were able to provide profiles in cases that would have previously been ruled inconclusive,” Sikorsky said.
And those items in Henry’s stolen Honda could now be analyzed further.
According to a Jupiter police report, the glove had 89 percent of the DNA contribution came on the glove came from Steward and 7 percent to Vasata. The last 4 percent belonged to an unknown contributor.
The frame of the rifle found by the car had 69 percent DNA contribution from Vasata, 25 percent from Steward, and 6 percent from an unknown person.
The hoodie found in the car had 53 percent of Steward’s DNA, 33 percent of Vasata’s and 14 percent belonged to a third person.
Police have not said if anyone else has been identified.
With new technology comes new questions and standards in court.
On Jan. 16, Steward’s attorneys filed a motion asking for information about the DNA technology and how the samples are kept, among other details.
Sikorsky said while there have been cases involving their work with STRmix since August, the analysts are mainly doing depositions at this point. In the meantime, she said, they’re also finishing presentations for the State Attorney’s Office and the Public Defender’s Office so they can have a better understanding of the technology during trials.
The new probabilistic genotyping software has come under fire in the courts across the world, but it also has been allowed by judges for use in Florida and other states.
In State of Florida v. Dwayne Cummings, Cummings wanted to exclude the STRmix DNA evidence from his Manatee County first-degree murder trial in 2017. Circuit Judge Hunter Carroll concluded “the State met its burden to demonstrate that probabilistic genotyping and the STRmix software are reliable and may be presented to the jury in this case.”
Another software program, TrueAllele, has come under fire for not releasing source code to be examined in cases.
In 2014, STRmix had its own issues in New Zealand courts after coding errors were detected. Since then, it released its mathematical equations to be examined.
Sikorsky said one reason the sheriff’s office picked STRmix over others like TrueAllele is because it’s “less of a black box.” STRmix provides equations and showed PBSO analysts during training how the calculations work.
“I could not rederive any of the equations they did (off the top of my head),” Sikorsky said laughing. “But they explained to us how the software program works, so we could translate that.”