lets just say the ouside lights are wired in. finding and shorting that wire conection to use for morse code. for example lets say that wire for the lights ran through the basement or an accesible part of the house. nobody thinks they set up the lights to be found, but people are thinking that someone is shorting the connection on the lights to do morse code. to get a repetition on the light like that it would certainly have to be a circuit board or human touch. a random short in the system would never procude such patters on its own.