  We use the spatially-resolved, multi-band photometry in the GOODS South field
acquired by the CANDELS project to constrain the nature of candidate Lyman
continuum (LyC) emitters at redshift z~3.7 identified using ultra-deep imaging
below the Lyman limit (1-sigma limit of ~30 AB in a 2" diameter aperture). In
18 candidates, out of a sample of 19 with flux detected at >3-sigma level, the
light centroid of the candidate LyC emission is offset from that of the LBG by
up to 1.5". We fit the SED of the LyC candidates to spectral population
synthesis models to measure photometric redshifts and the stellar population
parameters. We also discuss the differences in the UV colors between the LBG
and the LyC candidates, and how to estimate the escape fraction of ionizing
radiation (f_esc) in cases, like in most of our galaxies, where the LyC
emission is spatially offset from the host galaxy. In all but one case we
conclude that the candidate LyC emission is most likely due to lower redshift
interlopers. Based on these findings, we argue that the majority of similar
measurements reported in the literature need further investigation before it
can be firmly concluded that LyC emission is detected. Our only surviving LyC
candidate is a LBG at z=3.795, which shows the bluest (B-V) color among LBGs at
similar redshift, a stellar mass of M~2 x 10^9 Msun, weak interstellar
absorption lines and a flat UV spectral slope with no Lya in emission. We
estimate its f_esc to be in the range 25%-100%, depending on the dust and
intergalactic attenuation.
