Jmo, but if Welsh is one's first language then giving evidence in that language would be crucial. I teach groups of students through the medium of English, some of whom spoke Welsh at home and during primary school years, but English during high school. Whilst these students understand instruction in English, some struggle to communicate, in written and sometimes spoken form, finer points as they are attempting to translate the Welsh thoughts in their head to English. In these cases they write in Welsh and we translate to English whilst marking. The school teacher would probably have given her statement to the LE in Welsh and it would have been transcribed in Welsh. Important statements crucial in cases like these could not afford to have details lost in the translation of the witness, far better to capture the info in the witness' first language and then translate, using several translators if necessary. I don't think 'pride' necessarily comes into it, although we are proud of our language and culture here in Wales - I think giving evidence in one's first language is just common sense. IMHO.
As for the 3rd DNA on the shower curtain, clearly a woman had been in the house, sanitary towels can be seen on the bathroom windowsill in the evidence photos.