The case against Larry Taylor for driving under the influence was straightforward. In December 2010, he rear-ended an SUV in Northwest Wash­ington. He was slurring his words, according to police reports, and his blood alcohol level was 0.161, double the legal limit.

The case against him for the unregistered gun police found in his truck? Not so simple. In a January order, District of Columbia Superior Court Judge J. Michael Ryan found the police search of Taylor’s truck had been unlawful. The U.S. attorney’s office is appealing the ruling, which suppressed all evidence of the gun.

The case tackles a question attorneys say was left unanswered by the U.S. Supreme Court’s 2009 decision in Arizona v. Gant: When is it lawful for police to conduct a warrantless search of a vehicle after making a lawful arrest?

In Gant, the court held that warrantless searches of vehicles following lawful arrests “are per se unreasonable” under the Fourth Amendment. The ruling reversed nearly three decades of precedent that gave law enforcement wider latitude.

The high court carved out a few exceptions, though, including cases where it is “reasonable to believe” police might find evidence of the crime in the vehicle. Since then, state and federal courts across the country have tried to hammer out what the standards should be for a “reasonable” belief. It’s an issue the District of Columbia Court of Appeals has yet to decide.

In the case of Taylor, who pleaded guilty to the DUI and spent five days in jail, the government argued that police searched his truck because past experience taught them that they could often find evidence of a DUI — an open bottle of alcohol, for example — left in the vehicle. Given Taylor’s high blood-alcohol level, police also testified that they thought there was a good chance they would find whatever he had been drinking in his truck.

Ryan found that, if he followed the government’s logic, he would end up creating entire categories of cases, such as DUIs, where it’s assumed that warrantless searches are reasonable. That scenario would run too far afoul of the court’s intent in Gant, which was to limit such searches, Ryan wrote.

The government has argued that it is not advocating such a rule. Instead, the government claims that it’s reasonable for police to rely on past experience in deciding whether they think they might find evidence to support the arrest. The government also argues that there were other facts in Taylor’s case — his behavior and high blood-alcohol level — that led police to think a search was reasonable.

“The officers’ experience only confirmed their common-sense, reasonable belief that relevant evidence of appellee’s DUI offense would be found in the truck’s passenger compartment,” the government argued in its brief. Assistant U.S. Attorney David Goodhand is expected to argue the case. The U.S. attorney’s office, through spokesman William Miller, declined to comment.

Taylor’s attorney, Washington solo practitioner Jonathan Dailey, said in an interview that while it might be easier for law enforcement to have a “per se rule” green-lighting warrantless vehicle searches for certain types of arrests, “I don’t think it’s constitutional.” If the government wins on appeal, he said, “the exception to the Fourth Amendment has now swallowed the rule.”

The D.C. Court of Appeals will hear arguments on April 24.

Taylor, according to Dailey, was licensed to carry his gun in Virginia, but made the mistake of keeping it in his truck when he went into the District.

After he was arrested for the DUI and placed in handcuffs, officers searched his truck and found the gun in a locked glove compartment. They testified later that they were looking for his insurance information as well as evidence of drinking. Taylor was charged with carrying an unlicensed pistol and possessing an unregistered firearm and ammunition.

POLICE SAY THEY LACK CLARITY

Twenty months earlier, in April 2009, the Supreme Court had issued the Gant ruling. Kristopher Baumann, chairman of the D.C. police union, said Gant not only upended long-standing practices, but also that the litigation that followed left police officers unsure of what to do in situations like the one presented in Taylor’s case. “When you have lawyers and law professors arguing over these issues and it’s not clear to them, imagine the practical application on the street and an officer trying to apply it,” he said, adding that he thinks training has been too “ad hoc” given the complexity of the case.

A spokeswoman for the Metropolitan Police Department, Gwendolyn Crump, said in an e-mail that, after Gant, the department put together a mandatory online training module, placed information about the ruling in an internal training bulletin and incorporated it into current training programs, including as part of a lesson plan for recruits on laws of arrest.

John Wesley Hall Jr., former president of the National Association of Criminal Defense Lawyers, said he has found that training on Gant nationwide has been inadequate. But Hall, a criminal defense attorney in Little Rock, Ark., also thinks law enforcement has been resistant to change and that officers “still want to invade everybody’s privacy in a car search.”

The exception to Gant at issue in Taylor’s case came out of the Supreme Court’s 2004 ruling in Thornton v. U.S.,where the court found that police could conduct a warrantless search of a vehicle after a lawful arrest if it was “reasonable to believe” they would find evidence of the crime. As Ryan noted in his January order, the D.C. appeals court hasn’t defined what evidence police need to already have to meet the “reasonable to believe” standard for a warrantless search, but other courts have issued rulings that support both Taylor and the government’s positions.

Ryan found that the government’s “broad reading of Gant goes against the basic protections of the Fourth Amend­ment.” He added that “this approach would allow an officer to conduct a search of a vehicle under this narrow exception without relying on any facts specific to the actual case.”

The government maintains that police did have facts specific to Taylor’s case. Even if they didn’t, however, the government is arguing that courts have historically held that certain searches can be justified by the type of offense, such as a frisk when police believe a person is armed and dangerous. “Some crimes by their very nature are so suggestive of the presence of evidence that, barring special circumstances, a search is always reasonable,” the government wrote in its brief. “A DUI offense is such a crime.”

Dailey said a ruling in favor of the government would create a “slippery slope.” Law enforcement officials may find the process of getting a warrant inconvenient in a case like Taylor’s, he said, “and yet it’s a foundation of the Fourth Amendment experience. We can’t allow it to become obsolete because it’s inconvenient.”

Baumann said that while the government’s reading of Gant is how he understood the ruling, he’s just looking forward to settling the issue. “Our worst nightmare is we find evidence and it gets excluded and the bad guy walks free,” he said.

Zoe Tillman can be contacted at ztillman@alm.com.