SALT LAKE CITY — National Guardsman Matthew Johnson has been missing since September 20, according to Cottonwood Heights police. Multi-agency searches continue in northern Salt Lake County, and a former FBI agent said weather could become a factor.

“Most of the technology they use, radar detection, relies heavily on thermal sensors,” said retired agent Greg Rogers.

Johnson’s wife, Jennifer Gledhill, is accused of Johnson’s murder.

After weeks of searching, multiple agencies are still searching for Johnson’s body. Police officials tell FOX 13 News they have been searching since October 3.

Rogers, who worked at the FBI for 25 years, said the weather could impact the ongoing search.

“A decomposing body gives off a fair amount of heat and if the ground freezes, these technologies are not very effective,” he said.

With cooler temperatures heading toward Utah, future forensic analyzes could also be affected.

“Depending on the method of homicide, if there was a gun involved, it’s not going to have too much impact,” Rogers said. “But decomposition makes a big difference if it’s strangulation or something, so the sooner they find it, the better it will be for the medical examiners.”

Rogers commends the agencies for their hard work in finding Johnson’s body.

“They’ve dedicated a very good amount of resources. They’re taking this very seriously,” he said.