Spatially resolved measurements have been made of the deuterium Balmer series emission in the outer leg of the JET divertor using a high resolution spectrometer. At high density the excited states n=5-2 to 13-2 are observed and spectra obtained to the series limit. The high-n states are substantially broadened due to the Stark effect and there is a marked change in the continuum level between l £ 370 nm and l = 395 nm. Stark broadening is analysed to obtain radial distributions of the density across the outer target plate. The maximum density exceeds 5x1020 m-3 and is observed to be correlated with the strike point (either on or outside) prior to detachment.