We have a problem with cat and dog mess on our front path and garden-any suggestions?

Every day we have to clear up both dog and cat faeces from our concrete path, gravel garden or flower border. We have tried every deterrent and nothing stops them from using our garden as their own personal toilet. There are 4 dogs in the road. One goes everywhere on a lead, one stays put in its own garden, even when unsupervised but the other two next door are allowed to run free unsupervised and then loaded into the car to be taken out for a walk. We have caught one of the dogs on our property more than once but have not yet caught it making the mess. However the owner went away for two weeks and the cat and dogs were not around - no dog/cat mess at all. Within 12 hours of their return to the property we had cat/dog mess to clear up again. Any ideas how to deter them from doing this or how to find actual evidence so that I can politely ask the neighbour to exercise more control over her animals? It really is most unpleasant to have to clear up this mess day after day - sometimes twice a day and we are becoming desperate.