Robust Logic Circuit Design Tricks?
If it's a safety issue you can design your circuits so that two faults must happen before an output can be driven accidentally, as shown below.







simulate this circuit &ndash; Schematic created using CircuitLab

However, even with that, you need to worry about trace routing, connections, connectors and wiring shorts too. For example, in the circuit above, a short between the bottom of D3 and ground would cause unfortunate results.

If, on the other hand, you  want it to work despite a single fault, then that get's a lot more complicated.

Looking at analogsystemsrf's suggestion you may think you get some visibility into whether the and gates are working correctly.



HOWEVER, now you need to know if the OR gate is working... Worse, if the XOR gate fails you will either think there is a fault when there isn't, or not see the real fault. You also doubled the chance of failure by doubling the number of gates.. (Four times if you count the extra and gate). And what happens if the XOR gate failure mode is to pull an input high.... 

In the end, you are actually much farther away from fault tolerance than when you started. 

You can use backup systems, but, if you only have one backup system then the phrase "Man with two watches never knows the right time!" comes to mind. It is impossible to tell which is right. That's why three or more backup systems are needed to implement voting systems.

In general, critical systems are designed to "FAIL-SAFE" and be replaced. If however, replacement is a bit awkward... e.g. in space, deep sea, etc., multiple redundant systems are often employed. Either using a voting system, which of course needs it's own fault detection and recovery systems, or remotely switched in after a fail-safe halt.

However, please be aware, adding more circuitry does not make a device more reliable. In fact the opposite is true. Every component you add reduces the reliability. 

It may be more fault tolerant, but you will significantly reduce its "100% working" life.