Lens (z_L) and source (z_S) redshift distributions of the 9 QSO-ELG lens candidates, the 3 QSO-LAE lens candidates and the 49 remaining SLEs selected by the algorithm that were not shortlisted as QSO-LAE candidates (see Appendix A for some examples), with redshift are determined assuming either background Lyman-α or [O II] emission. In the case of QSO-LAEs, our selection method seems to favour low redshift QSOs and high-redshift background sources. QSO-ELG candidates however have both low lens and source redshifts. The lower and upper boundaries on the source redshift are due to the limited range of the SDSS spectrograph. The dotted line indicates the z_S >  z_L limit for background object detections.