If you confront a threatening suspect who has a large knife Rambo knife in his hand, you’ll see it, right? How about your partner?

Don’t be too quick to answer yes.

Consider the following actual training experience:

The scenario took place in a warehouse where officers were called to investigate a reported nighttime break-in. Upon arrival, they first had to deal with the scared and armed warehouse manager, role-played by a local judge, and then with a drunken ex-employee, played by a supervisor, who was furious at having lost his job. The ex-employee was armed with a dummy hand grenade and a large 8-inch-long, 3-inch-wide knife…in this case, thankfully, made of rubber.

The ex-employee concealed the knife by cupping the hilt in the curled tips of his fingers and resting the blade against his forearm. He was wearing a short-sleeved tee shirt, so his arms were fully exposed.

As the officers engaged the ex-employee, he put on a drunken rage act, threatening to “blow up the damn place” while stumbling around wildly and waving the grenade with his left hand while making it clear he had no problem dying. His plan was to divert the officers’ attention from the large knife he had concealed in his right hand, and it worked.

During one of the run-throughs of the scenario, one officer ordered the ex-employee to place his hands in the air and turn around, which he did. However, the supervisor playing the role noted that the officer failed to notice that when he turned, he always kept the backs of his arms—where the knife was visible—away from him.

The officer then ordered the suspect to spread-eagle on the floor. As he moved in to cuff him, the supervisor/role player was able to turn over and slash up into his groin and leg. The officer was so startled he short-stroked his semi-auto trigger causing the gun to malfunction.

A cover officer, who had also failed to spot the knife, tried to move in to grab the grenade and as he did, the ex-employee was able to knock his weapon to the side and flip the knife down in a beheading movement. The officer’s reaction was to freeze when he saw the blade slashing down toward his exposed neck. In after-scenario debriefings that officer admitted he never knew the knife was there until he felt it touch his skull.

In another running of the scenario, one of two officers was standing almost directly behind the ex-employee providing cover while his partner made contact. He said he never saw the knife either, even though it would have been fully visible from that vantage point. Evidently, he tunnel-visioned in on the extended hand holding the grenade.

And in yet another running, an officer had the suspect spread eagle on the floor and when he came in to cuff, the ex-employee “stabbed” him in the ribs and took his gun. Because of the suspect’s positioning, the partner officer couldn’t fire without hitting his fellow officer.

The supervisor who ran the scenario noted that each of the officers who failed to detect the knife overlooked three tactical cautions you should keep in mind:

1. If you can’t see the tips of all fingers when an offender’s arms are hanging at his sides, you must assume he is palming something.

2. If you have the offender turn around, make sure you see all of his body.

3. If you spread eagle an offender, make sure his arms are out to the side with palms up.

The supervisor, who has extensive martial arts training, said he chose a knife for this scenario because he believed they’re often taken too lightly. He felt that some officers underestimate people armed with knives but, he cautioned, they must remember that someone who chooses a knife as a weapon may have a very different mindset than others. “The knife fighter’s choice of weapon alone tells you that this person does not mind getting in close and dirty,” he said. “Close-quarter combat is very unsettling to most officers, but don’t skimp on training in this area.”

Interesting side note: Each officer participating had their blood pressure taken before being sent into the warehouse and then after the scenario was complete. After running through the encounter, some trainees’ blood pressure reading rose by 60 points.