Thermal imaging devices measure heat emanating from a structure by using optical electronic sensors which can read the thermodynamic characteristics of the target. Police often use thermal imagers to detect heat generated by indoor marijuana growing operations. The majority of U.S. courts have ruled that the warrantless use of these devices does not raise Fourth Amendment concerns; they are used beyond the curtilage of the property and thus do not intrude onto or into the targeted property. However, once the operator targets the suspected structure in an effort to “see” the heat patterns on the building’s exterior, constitutional issues under the Fourth Amendment are raised. The 9th and 10th Federal circuits hold that using a thermal imager requires a warrant since the device can see beyond walls. The remaining circuits reason that, since the device reads waste heat, a warrant is not required.