away from home 7am to 6pm). 
If you want a dog to guard your house, you better have a 100% recall. Proper guard dogs are highly trained animals, they're not just naturally protective dogs that are allowed to behave however they want. Allowing that behavior without control is asking for a lawsuit when that dog feels it should bite or threaten someone it shouldn't (like a cop coming to your door or yard to investigate a call).
Many cops will shoot dead any medium or big dog that approaches them if they enter your property and it's behaving in a threatening way towards them (barking/growling). They will generally not wait to 'be sure' your dog isn't about to attack them before they defend themself, especially if it's a 'scary looking' breed. Most cops are not dog experts, they can't tell if a dog is genuinely dangerous or just being defensive.
Really, if you have a big dog in the first place, that is already a deterrent. Most criminals will see it and move on, they do not stop to check if the dog is friendly or not, they simply won't bother with the house at all. Most thieves are cowards. =P
Many cops will shoot dead any medium or big dog that approaches them if they enter your property and it's behaving in a threatening way towards them (barking/growling). They will generally not wait to 'be sure' your dog isn't about to attack them before they defend themself, especially if it's a 'scary looking' breed. Most cops are not dog experts, they can't tell if a dog is genuinely dangerous or just being defensive.
Really, if you have a big dog in the first place, that is already a deterrent. Most criminals will see it and move on, they do not stop to check if the dog is friendly or not, they simply won't bother with the house at all. Most thieves are cowards. =P
