Taking a closer look at the work of Willmar Police Department's cold case team on the "Mae" Herman homicide

Over the course of two weeks, members of the Willmar Police Department cold case team eliminated suspects in the stabbing death of Mabel "Mae" Agnes Boyer Herman in 1974 before securing DNA evidence that tied Algene LeeslandVossen to the 46-year-old cold case.

Sgt. Chad Nelson, left, and Officer Jason Evans flip through case reports dating back to the mid 1970’s that they read to help determine the primary suspect for the killing of Mabel "Mae" Agnes Boyer Herman this past July. Erica Dischino / West Central Tribune
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WILLMAR — A cold case team from the Willmar Police Department successfully connected the dots last month to bring a murder charge against Algene Leeland Vossen, 79, for the brutal stabbing death of Mabel "Mae" Agnes Boyer Herman in 1974.

The team members, using DNA evidence and old-fashioned detective work, were able to eliminate suspects until officially being able to tie Vossen to the Herman homicide by getting a match to blood found on the sweater she was wearing when she was stabbed at least 38 times on the night of Jan. 27, 1974.

Vossen was arrested July 23 at his home in Sioux Falls, South Dakota, and is currently in the Minnehaha County Jail in Sioux Falls awaiting extradition to face a second-degree murder charge in Kandiyohi County.

While the idea of setting up a cold case team to review cases in Willmar had been floating around the department for a few years, it was around March of this year that Willmar Police Chief Jim Felt gave the word to assemble officers to tackle some of the cases that have eluded justice for years.

"When I became chief, I knew that this Mae Herman case was unsolved and we had been talking as a group at some of our strategic planning meetings that, at some time, when we had enough personnel and enough time, we wanted to get people together and do a cold case review," Felt said. "That Mae Herman case was probably the primary one."


Detective Sgt. Chad Nelson was given the responsibility of finding officers for the task, specifically ones who were experienced, had good investigative skills and had broad knowledge about the job along with expertise.

Part of Nelson's considerations involved maintaining proper staffing levels for the rest of the department, particularly the detective unit because the department still had ongoing active cases.

The arrival of the COVID-19 pandemic and the ensuing shutdowns, including schools, freed up school resource officers to take part in the exercise. That, coupled with an officer who was on light duty due to an injury, allowed Nelson to grab senior officers with good reporting and investigative skills, along with good instincts.

"There wasn't going to be any training here," Nelson said. "This was going to be reviewing and working the case."

Digging in

Over a two-week period, the cold case team, gathered in the department's meeting room, looked over the evidence in the case, including some well-preserved physical evidence.

"I've been here 23 years and I've never seen this case file and never picked it up," Nelson said. "I've heard about it from other officers and other detectives but never had the opportunity. So I was learning just as much as the officers were as we were going through it."

As the team started going through the files, Officer Jason Evans suggested the pages be read aloud to the group instead of each team member making copies and going at their own pace.

"It just felt like it'd be better if we just took turns reading the reports and taking notes as we went," Evans said. "We could have conversations about things as we were reading the reports and discuss certain pieces of evidence as we went along."


But as the officers were going through hundreds of pages of documents, they had to sift through a completely different system of reporting. For example, everything was listed chronologically in the 1974 reports, and names would be listed throughout, rather than organized at the top for easy reference.

"So it was just getting through and understanding who all the people were involved,” Nelson said.

Luckily, a retired Willmar officer had gone through the case around 1979 and organized the file and put page numbers on the papers.

"It made it a lot easier for us," Evans said.

The team also enlisted the help of the department's administrative secretary, who scanned in all the documents so they would have digital copies in case anything were to happen to the original reports.

The team ended up creating an entire new file for the case, organized and in compliance with their current reporting requirements.

Reading the reports out loud and the previous organization helped the team visualize what they would see for physical evidence, which in turn helped them better analyze it.

The evidence

The team did have to repackage some of the evidence to meet current standards as well as take some high-definition photos and run a black light over the items to identify bodily fluids.


"Going through the evidence I think was probably the most interesting part of it and seeing how well it was packaged," Nelson said.

As far as the team landing on Vossen as the primary suspect, it was a gradual process, according to Evans.

Officers at the time had focused on a juvenile male that lived nearby.

Statements that Vossen made at the time didn't help him, according to Nelson, and officers had focused on him initially.

"You can see the officers from back then, they were going through a process of elimination," Nelson said. "Pulling names from past offenders and Vossen's name was mentioned early on because of being a window peeper."

A Feb. 17, 1974, report stated Vossen had been caught window peeping and had been interviewed by a detective at the time and then again on Feb. 19 about Herman and his whereabouts. Law enforcement also followed up around May of that year and talked with Vossen's girlfriend.

Vossen said that he had been out barhopping the night of Herman's death and he only knew what had been in the newspaper or talked about in town.

"The only thing that was missing was there was no follow-up done with the bartenders where Vossen said he'd been," Nelson said.

As the team continued following the evidence left to them by their predecessors, Vossen became a subject of interest.

"Initially, they had a different suspect that they were looking into pretty seriously, and then when Vossen came around, the evidence just kind of built up and built up and built up," Evans said. "The more we read, the more information that came in on him, the first suspect kind of melted away."

While Vossen was a subject of interest, the team relied on DNA evidence to officially eliminate someone as a suspect.

DNA analysis was more primitive in 1974, according to Nelson, with officers needing a lot of blood to basically get a blood type match.

In 2020, DNA analysis has advanced to the point at which, with enough evidence, law enforcement is able to match it to specific people.

Nelson said they had DNA samples from other suspects sent in to the Minnesota BCA Crime Lab along with Herman's sweater and pants.

"Fortunately enough, we were able to eliminate two suspects right off the bat when they found blood from an unidentified male on her sweater," Nelson said.

With the assistance of the South Dakota Division of Criminal Investigation, the team was able to secure and serve a search warrant for Vossen's DNA evidence at his home in Sioux Falls on July 7. A brief interview also took place and Vossen stuck to his previous statements.

On July 17, two saliva swabs was all it took for the BCA crime lab to confirm Vossen's DNA was the same DNA found on Herman's sweater.

Felt said when he got a notification that the BCA crime lab had results, he couldn't get logged in fast enough.

"When I pulled up the results and printed it out, Sgt. Nelson was on a vacation day and I thought he would not mind me calling him on a day off to let him know the results are there," Felt said.

It's not final yet

While there's an obvious sense of excitement with being able to finally charge someone for this crime, Nelson remains cautious as the wheels of justice turn.

"For me, Vossen is innocent until proven guilty," Nelson said. "It's a step and it's moving forward, but the case isn't done until he's back here and he goes to trial or pleads guilty or he's found not guilty."

Since Vossen's arrest, Felt said his first phone call was to a surviving relative to Herman, a granddaughter in the Twin Cities, to give her the news, but the second phone call was to the juvenile suspect police had initially focused on.

"It was equally rewarding to tell him that after all these years living under that shadow that he had been officially eliminated as a suspect through DNA analysis."

Mark Wasson has been a public safety reporter with Post Bulletin since May 2022. Previously, he worked as a general assignment reporter in the southwest metro and as a public safety reporter in Willmar, Minn. Readers can reach Mark at
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