Final answer:
The emission spectrum would provide more reliable results in identifying an unknown substance found at a crime scene.
Step-by-step explanation:
The method that would provide more reliable results in identifying an unknown substance found at a crime scene would be the emission spectrum.
The flame test relies on observing the color of the flame produced when the unknown substance is heated. Each element emits a characteristic color when heated, so by comparing the color produced by the unknown substance to a known emission spectrum, one can determine the elements present.
On the other hand, the emission spectrum involves passing light emitted by the unknown substance through a prism or a spectrometer. This disperses the light into its component wavelengths, forming a spectrum. By comparing the emission spectrum of the unknown substance to known emission spectra of elements, one can determine the elements present in the unknown substance more accurately.