The “10 deadly errors” hung in my locker every day of my career. I originally obtained them from the book, "...officer down, code three" by LAPD homicide detective Pierce Brooks.

After attending “too many” police funerals, Brooks compiled a list of errors that were being repeatedly committed in officer-down cases.

Here is my take on those original 10, as well as two more I’ve taken the liberty of adding in order to make the “dirty dozen.”

If you find one suspect, one weapon, one explosive device, one of anything dangerous, do not relax. Continue the search for more. (Photo/Pixabay)

1. Attitude

If you fail to keep your mind on the job for any reason, you may miss critical indicators of impending danger. Having an unhealthy attitude can also cause an officer to slip into such a malaise they are susceptible to committing other errors as a matter of routine.

Any coach will tell their players that attitude can make the difference between a win and a loss in any game. This could apply to law enforcement, except for the fact that police work is not a game and losing is not an option.

2. Tombstone Courage

When you wear a badge every day your courage is a given and does not need to be proven on every call. In some cases, police work is best done when done as a team. Do not hesitate to enthusiastically give and patiently wait for backup.

Sometimes it’s just plain smart to slow things down or even disengage.

3. Not Enough Rest

An old veteran told a rookie, “To survive this career all you have to do is pay attention!”

Being alert is a necessity in law enforcement, and you can’t do that when you are sleepy or asleep.

4. Taking a Bad Position

On every call, with every suspect, on every approach, you must evaluate your position constantly. You must know how to use cover, concealment, barriers and relative positioning to your advantage.

5. Missing Danger Signs

Prior to most attacks, there are usually indications that an assault is imminent. Recognize changes in a suspect’s muscular tension, an increase in respirations, modified offensive stances, offensive hand positioning, glances toward exits, looking for witnesses, checking out your weapon, furtive movements, signaling toward accomplices and verbal threats to do you harm. Learn to recognize danger signs and never explain them away. Avoid developing technological tunnel vision.

When you are in contact with the public, look up and look out. Get your head out of your apps!

6. Failure to Watch the Suspect’s Hands

The hands kill. Throughout every call and contact, “WATCH THE HANDS!”

7. Relaxing Too Soon

If you are able to convince yourself that alarms are false before you arrive on scene, you are probably an officer who is “routinely” relaxing too soon on most of your contacts.

Officers must resist the tendency to relax when they confront compliant suspects, because feigning compliance is a common criminal tactic. If you find one suspect, one weapon, one explosive device, one of anything dangerous, do not relax. Continue the search for more. Remember, nothing is “routine.”

8. Improper Use or No Use of Handcuffs

If a suspect is arrested and transported, policies all over the nation require that they be handcuffed. Officers should be as proficient with multiple tactical handcuffing techniques as they are with their firearms.

9. No Search or Poor Search

In today’s world, criminals can buy clothes that have secret compartments, within which they can conceal weapons, drugs, contraband and fruits of a crime. It is imperative that every arrested suspect be searched thoroughly. Search the suspect’s person incident to arrest as well as the lunge area. Then search them again before you take them into the jail. Additionally, you must search every suspect turned over to you for transport by other officers.

10. Dirty or Inoperable Weapon

You should neither leave firearms training, nor hit the streets with a dirty weapon. Some officers never take the time to truly learn how to field strip their weapon and when that happens they stop properly cleaning their weapons. Before beginning your shift make certain long guns are “squad ready.” There should be no firearm in your squad that you can’t quickly access and bring into the fight under stress. Take care of your weapons and they will take care of you.

Additionally, a weapon is only operable if an officer is mentally prepared to use it, when a life depends on it. Are you prepared?

Those are the original 10. Here are two new deadly errors I’ve added to the list.

11. Failure to Wear a Vest or a Seatbelt

Vests and seat belts have saved thousands of officers’ lives, but they can only save your life if you are wearing them.

12. Failure to Maintain Physical/Emotional Fitness

There is an urgent need for police officers to maintain a high level of fitness to face both the considerable physical and emotional challenges this career has to offer. To enhance your physical fitness level, train, run, lift and stretch at least three times a week. To maintain emotional fitness, laugh, love, work, play and pray, while striving to maintain a positive perspective on your life and career.

Now with that said, you may hit the streets...and in the words of Sergeant Phil Esterhaus, “Be careful out there!”

This article, originally published on 02/24/2014, has been updated.