Spare keys. Homeowners often hand them out to neighbors, house sitters and to contractors doing renovations. Spare keys are also given to children who may lose them and some may even remain in the possession of old lovers. Unfortunately, left in the wrong hands, a spare key could possibly be used to harm you.

For example, a handyman was convicted in 2014 of murdering a woman in West Miami-Dade. Prior to the murder, the man had once worked on the woman's home as a contractor and had been given a spare key. Investigators discovered that he had used this spare key to enter the woman's home and had then robbed and beaten her to death. 

Because missing spare keys are always a liability, it is important that you change or re-key the locks on your home immediately if one is lost. But there are also other circumstances, such as the following five situations, when you should also consider having your locked changed or re-keyed:

You Move Into a New House

When you move into a new home, you should consider hiring a professional locksmith because:

• You have no idea who may still have access to spare keys to your home. The former homeowners may have left spares with relatives, neighbors, dog walkers and others. So it is important to have your entire home rekeyed.  
• The locks or doorknobs may be in bad shape, so you may have to install new locks instead of just rekeying them.
• Your home's lock system may be inadequate. You may want to have a locksmith add deadbolts or other more secure locking mechanisms to your doors.

And while it may seem like overkill to have a brand-new home rekeyed, it may be necessary. Why?  Because you have no idea what contractors may have had access to the lock box key that was on your home before you owned it.

Unfortunately, it is extremely easy to make copies of keys these days. For example, Wired recently tested several new Apps that allowed them to make a copy of a key simply by taking a photo of it with a smartphone and then sending that information to a company, which can then make a 3-D print copy of the key. With this method, a homeowner -- who still has the key-- will have no idea that a spare has even been made. 

You Are Involved in a Bad Breakup

Chances are that your old lover may never use the key to your house, but it's always better to be safe than sorry. Bad breakups tend to bring out the worst in people and even the most mild-mannered individuals can sometimes go over the edge. They could, for example, use the key to enter your home and trash it, or they might decide to "steal" items they believe rightfully belong to them. Or worse, they could decide to use your key to enter your home unexpectedly to talk to you face to face. 

A Family Who Has Your Key is Having "Issues"

Unfortunately, your neighbor's problems can quickly becomes your own. For instance, if your neighbor's teenager has suddenly developed an addiction to prescription drugs, they might be tempted to use a spare key that you left with your neighbor in order to break into your home and search it for medications. So if you know of a neighbor or a relative that is having family difficulties, it may be wise to diplomatically ask for your spare back. If the person cannot find the key, then it is time to consider having your locks re-keyed by a locksmith. 

While re-keying a home may sound like a drastic step, it could bring you a lot of peace of mind, especially when it comes to these three situations.