The majority of those killed by Georgia police officers in 2017 and 2018 had drugs in their system, including cocaine, meth and marijuana, according to the GBI.

Of the 61 killed, 40 tested positive for a variety of drugs and tests were pending on six additional cases, the toxicology data obtained by The Atlanta Journal-Constitution showed. Toxicology testing was either not completed or not submitted to the GBI for six of the autopsies.

With the number of deadly officer-involved shootings on track to double 2017’s total, law enforcement leaders are looking for answers, GBI Director Vernon Keenan said during a recent interview. And drugs are a key issue he said.

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In 2017, 30 Georgians were shot to death by Georgia officers and one person was killed by a Taser, according to the GBI. So far in 2018, 30 people have been shot to death by officers.

“When you look at the underlying facts of the instances, the officers were usually justified in using force because they were dealing with a very difficult person,” Keenan said.

Critics say that police should do more to deescalate tense situations. And the toxicology records did not indicate what role the drugs played in the encounters.

Toxicology testing is a routine part of autopsies conducted by the GBI in use-of-force cases involving officers. Though every use of force case is different, experts believe drugs and mental health are two factors fueling the increase in number of officer-involved shootings.

“Drugs are a factor in a majority of the cases,” Nelly Miles, GBI spokeswoman, said Monday.

Marijuana was the most popular drug used by those in deadly altercations with police, followed by amphetamines and methamphetamines. Sixteen people tested positive for marijuana and 14 had amphetamines or meth in their system, records showed.

“When you talk about volume, there’s more meth out there than anything else except marijuana,” Miles said. “Methamphetamine does cause people to respond violently.”

Methamphetamine is stimulant drug that is chemically similar to amphetamine, which is used to treat ADHD and narcolepsy, according to the National Institute on Drug Abuse. Meth is highly addictive and long-term use can cause violent behavior, paranoia and hallucinations.

Not all of the drugs found in those killed by officers were illicit, though the quantities found during toxicology testing were not released. Various prescription drugs, including the pain medication Tramadol, the sedative Alprazolam (commonly known as Xanax), and Haloperidol, an antipsychotic medication, were also found in some investigations.