Old Mate "May" have taken some cough medicine But after 40min the underlying alcohol level has shown up on the breathalyser.
0.071 is a very high reading so Old Mate must have drank a couple of large bottles of cough medicine to achieve that high level which is equivalent to about 6-8 beers in a couple of hours.
Lots of people self test before a breatho and will try anything to beat the reading, A good breakfast and plenty of water will bring a low level reading down to zero's in under an hour But many try to "Mask" the reading by using cough medicine and other things.
I call BS on this particular "Cough Medicine" excuse.

