Hi there I am currently researching the Druce/Portland case. If you can get a second hand copy I recommend 'The Druce-Portland Case' by Theodore Besterman published in 1935. Also the contemporary newspapers have a wealth of information. There is an archive of papers at Nottingham University. I should mention that you won't find a birth certificate for Thomas Druce because birth certificates were not introduced in the UK till 1837. What you might be able to find is a baptismal record.